Water dispersible polythiophenes made with polymeric acid colloids

ABSTRACT

Compositions are provided comprising a continuous liquid aqueous medium having dispersed therein a polydioxythiophene and at least one colloid-forming fluorinated polymeric acid. Films from invention compositions are useful as buffer layers in organic electronic devices, including electroluminescent devices, such as, for example, organic light emitting diodes (OLED) displays.

RELATED APPLICATION DATA

This application is a continuation application and claims priority under35 U.S.C. §120 from U.S. application Ser. No. 12/181,609 (filed on 29Jul. 2008, now U.S. Pat. No. 8,585,931); which in turn is a divisionalapplication and claims priority under 35 U.S.C. §120 from U.S. patentapplication Ser. No. 10/669,494 (filed on 24 Sep. 2008, now U.S. Pat.No. 7,431,866); which claims the benefit of U.S. Application Ser. Nos.60/464,369 (filed on 22 Apr. 2003) and 60/413,202 (filed on 24 Sep.2002), all of which are incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The invention relates to aqueous dispersions of electrically conductingpolymers of thiophene, wherein the electrically conducting polymer issynthesized in the presence of polymeric acid colloids.

BACKGROUND OF THE INVENTION

Electrically conducting polymers have been used in a variety of organicelectronic devices, including in the development of electroluminescent(EL) devices for use in light emissive displays. With respect to ELdevices, such as organic light emitting diodes (OLEDs) containingconducting polymers, such devices generally have the followingconfiguration:

-   -   anode/buffer layer/EL polymer/cathode

The anode is typically any material that has the ability to inject holesinto the otherwise filled π-band of the semiconducting, EL polymer, suchas, for example, indium/tin oxide (ITO). The anode is optionallysupported on a glass or plastic substrate. The EL polymer is typically aconjugated semiconducting polymer such as poly(paraphenylenevinylene) orpolyfluorene. The cathode is typically any material (such as, e.g., Caor Ba) that has the ability to inject electrons into the otherwise emptyπ*-band of the semiconducting, EL polymer.

The buffer layer is typically a conducting polymer and facilitates theinjection of holes from the anode into the EL polymer layer. The bufferlayer can also be called a hole-injection layer, a hole transport layer,or may be characterized as part of a bilayer anode. Typical conductingpolymers employed as buffer layers include polyaniline andpolydioxythiophenes such as poly(3,4-ethylenedioxythiophene) (PEDT).These materials can be prepared by polymerizing aniline ordioxythiophene monomers in aqueous solution in the presence of a watersoluble polymeric acid, such as poly(styrenesulfonic acid) (PSS), asdescribed in, for example, U.S. Pat. No. 5,300,575 entitled“Polythiophene dispersions, their production and their use.” A wellknown PEDT/PSS material is Baytron®-P, commercially available from H. C.Starck, GmbH (Leverkusen, Germany).

The aqueous electrically conductive polymer dispersions synthesized withwater soluble polymeric sulfonic acids have undesirable low pH levels.The low pH can contribute to decreased stress life of an EL devicecontaining such a buffer layer, and contribute to corrosion within thedevice. Accordingly, there is a need for compositions and buffer layersprepared therefrom having improved properties.

Electrically conducting polymers also have utility as electrodes forelectronic devices, such as thin film field effect transistors. In suchtransistors, an organic semiconducting film is present between sourceand drain electrodes. To be useful for the electrode application, theconducting polymers and the liquids for dispersing or dissolving theconducting polymers have to be compatible with the semiconductingpolymers and the solvents for the semiconducting polymers to avoidre-dissolution of either conducting polymers or semiconducting polymers.The electrical conductivity of the electrodes fabricated from theconducting polymers should be greater than 10 S/cm (where S is areciprocal ohm). However, the electrically conducting polythiophenesmade with a polymeric acid typically provide conductivity in the rangeof ˜10⁻³ S/cm or lower. In order to enhance conductivity, conductiveadditives may be added to the polymer. However, the presence of suchadditives can deleteriously affect the processability of theelectrically conducting polythiophene. Accordingly, there is a need forimproved conductive polythiophenes with good processability andincreased conductivity.

SUMMARY OF THE INVENTION

Compositions are provided comprising aqueous dispersions ofpolythiophenes and at least one colloid-forming polymeric acid. Theinvention compositions are useful as buffer layers in a variety oforganic electronic devices, such as for example, organic light emittingdiodes (OLEDs) and in combination with conductive fillers, such as metalnanowires or carbon nanotubes, in applications such as drain, source, orgate electrodes in thin film field effect transistors.

In accordance with another embodiment of the invention, there areprovided organic electronic devices, including electroluminescentdevices, comprising buffer layers of the invention compositions that arecast.

In accordance with still another embodiment of the invention, there areprovided methods for synthesizing aqueous dispersions of polythiophenesand at least one colloid-forming polymeric acid. A method of producingan aqueous dispersion of polythiophene and at least one colloid-formingpolymeric acid, comprising:

-   -   (a) providing a homogeneous aqueous mixture of water and        thiophene;    -   (b) providing an aqueous dispersion of the colloid-forming        polymeric acid;    -   (c) combining the thiophene mixture with the aqueous dispersion        of the colloid-forming polymeric acid, and    -   (d) combining a oxidizer and a catalyst, in any order, with the        aqueous dispersion of the colloid-forming polymeric acid before        or after the combining of step (c).

Other embodiments are described in the detailed description of thisinvention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a cross-sectional view of an electronic device thatincludes a buffer layer according to the invention.

FIG. 2 illustrates a cross-sectional view of a thin film field effecttransistor that includes an electrode according to the invention.

FIG. 3 illustrates the change in conductivity of PEDT/Nafion® films withthe ratio of oxidizer to monomer in the polymerization reaction.

FIG. 4 illustrates the change in conductivity of PEDT/Nafion® films withthe ratio of Nafion® to monomer in the polymerization reaction.

FIG. 5 illustrates the operation lifetime of OLED devices with greenlight-emitting polymers.

FIG. 6 illustrates the operation lifetime of OLED devices with redlight-emitting polymers.

FIG. 7 illustrates the operation lifetime of OLED devices with bluelight-emitting polymers.

FIG. 8( a) through FIG. 8( d) illustrate the effect of the pH of thePEDT/PSSA buffer layer on OLED device performance.

FIG. 9( a) through FIG. 9( c) illustrate the effect of the pH of thePEDT/Nafion® buffer layer on OLED device performance.

FIG. 10 illustrates the change in ITO thickness when immersed indispersions of PEDT/Nafion® or PEDT/PSSA.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment of the invention, compositions are provided comprisingaqueous dispersions of polythiophenes, including, polydioxythiophenes,and colloid-forming polymeric acids. As used herein, the term“dispersion” refers to a continuous liquid medium containing asuspension of minute particles. In accordance with the invention, the“continuous medium” is typically an aqueous liquid, e.g., water. As usedherein, the term “aqueous” refers to a liquid that has a significantportion of water and in one embodiment it is at least about 40% byweight water. As used herein, the term “colloid” refers to the minuteparticles suspended in the continuous medium, said particles having ananometer-scale particle size. As used herein, the term“colloid-forming” refers to substances that form minute particles whendispersed in aqueous solution, i.e., “colloid-forming” polymeric acidsare not water-soluble.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having” or any other variation thereof, areintended to cover a non-exclusive inclusion. For example, a process,method, article, or apparatus that comprises a list of elements is notnecessarily limited to only those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Also, use of the “a” or “an” are employed to describe elements andcomponents of the invention. This is done merely for convenience and togive a general sense of the invention. This description should be readto include one or at least one and the singular also includes the pluralunless it is obvious that it is meant otherwise.

It has been discovered that aqueous dispersions of electricallyconductive polythiophene and, specifically, poly(dioxythiophenes) can beprepared when thiophene monomers including dioxythiophene monomers, arepolymerized chemically in the presence of colloid-forming polymericacids. Further, it has been discovered that use of a polymeric acid thatis not water soluble in preparation of an aqueous dispersion of thepolythiophenes or poly(dioxythiophenes) yields a composition withsuperior electrical properties. One advantage of these aqueousdispersions is that the electrically conductive minute particles arestable in the aqueous medium without forming a separate phase over along period of time before a use. Moreover, they generally do notre-disperse once dried into films.

Compositions according to one embodiment the invention contain acontinuous aqueous phase in which the polydioxythiophene andcolloid-forming polymeric acid are dispersed. Polydioxythiophenescontemplated for use in the practice of the present invention have thestructure:

wherein:

-   -   R₁ and R₁′ are each independently selected from hydrogen an        alkyl having 1 to 4 carbon atoms,    -   or R₁ and R₁′ taken together form an alkylene chain having 1 to        4 carbon atoms, which may optionally be substituted by alkyl or        aromatic groups having 1 to 12 carbon atoms, or a        1,2-cyclohexylene radical, and    -   n is greater than about 6.

Thiophenes of this invention have the same general structure as providedabove, wherein R₁ and R₁′ are substituted for the “OR₁O′” and “OR₁′”substituents.

In a particular embodiment, R₁ and R₁′ taken together form an alkylenechain having 1 to 4 carbon atoms. In another embodiment, thepolydioxythiophene is poly(3,4-ethylenedioxythiophene).

Colloid-forming polymeric acids contemplated for use in the practice ofthe invention are insoluble in water, and form colloids when dispersedinto an aqueous medium. The polymeric acids typically have a molecularweight in the range of about 10,000 to about 4,000,000. In oneembodiment, the polymeric acids have a molecular weight of about 100,000to about 2,000,000. Colloid particle size typically ranges from 2nanometers (nm) to about 140 nm. In one embodiment, the colloids have aparticle size of 2 nm to about 30 nm. Any polymeric acid that iscolloid-forming when dispersed in water is suitable for use in thepractice of the invention. In one embodiment, the colloid-formingpolymeric acid is polymeric sulfonic acid. Other acceptable polymericacids include polymer phosphoric acids, polymer carboxylic acids, andpolymeric acrylic acids, and mixtures thereof, including mixtures havingpolymeric sulfonic acids. In another embodiment, the polymeric sulfonicacid is fluorinated. In still another embodiment, the colloid-formingpolymeric sulfonic acid is perfluorinated. In yet another embodiment,the colloid-forming polymeric sulfonic acid is aperfluoroalkylenesulfonic acid.

In still another embodiment, the colloid-forming polymeric acid is ahighly-fluorinated sulfonic acid polymer (“FSA polymer”). “Highlyfluorinated” means that at least about 50% of the total number ofhalogen and hydrogen atoms in the polymer are fluorine atoms, an in oneembodiment at least about 75%, and in another embodiment at least about90%. In one embodiment, the polymer is perfluorinated. The term“sulfonate functional group” refers to either to sulfonic acid groups orsalts of sulfonic acid groups, and in one embodiment alkali metal orammonium salts. The functional group is represented by the formula —SO₃Xwhere X is a cation, also known as a “counterion”. X may be H, Li, Na, Kor N(R₁)(R₂)(R₃)(R₄), and R₁, R₂, R₃, and R₄ are the same or differentand are and in one embodiment H, CH₃ or C₂H₅. In another embodiment, Xis H, in which case the polymer is said to be in the “acid form”. X mayalso be multivalent, as represented by such ions as Ca⁺⁺, and Al⁺⁺⁺. Itis clear to the skilled artisan that in the case of multivalentcounterions, represented generally as M^(n+), the number of sulfonatefunctional groups per counterion will be equal to the valence “n”.

In one embodiment, the FSA polymer comprises a polymer backbone withrecurring side chains attached to the backbone, the side chains carryingcation exchange groups. Polymers include homopolymers or copolymers oftwo or more monomers. Copolymers are typically formed from anonfunctional monomer and a second monomer carrying the cation exchangegroup or its precursor, e.g., a sulfonyl fluoride group (—SO₂F), whichcan be subsequently hydrolyzed to a sulfonate functional group. Forexample, copolymers of a first fluorinated vinyl monomer together with asecond fluorinated vinyl monomer having a sulfonyl fluoride group(—SO₂F) can be used. Possible first monomers include tetrafluoroethylene(TFE), hexafluoropropylene, vinyl fluoride, vinylidine fluoride,trifluoroethylene, chlorotrifluoroethylene, perfluoro(alkyl vinylether), and combinations thereof. TFE is a preferred first monomer.

In other embodiments, possible second monomers include fluorinated vinylethers with sulfonate functional groups or precursor groups which canprovide the desired side chain in the polymer. Additional monomers,including ethylene, propylene, and R—CH═CH₂ where R is a perfluorinatedalkyl group of 1 to 10 carbon atoms, can be incorporated into thesepolymers if desired. The polymers may be of the type referred to hereinas random copolymers, that is copolymers made by polymerization in whichthe relative concentrations of the comonomers are kept as constant aspossible, so that the distribution of the monomer units along thepolymer chain is in accordance with their relative concentrations andrelative reactivities. Less random copolymers, made by varying relativeconcentrations of monomers in the course of the polymerization, may alsobe used. Polymers of the type called block copolymers, such as thatdisclosed in European Patent Application No. 1 026 152 A1, may also beused.

In one embodiment, FSA polymers for use in the present invention includea highly fluorinated, and in one embodiment perfluorinated, carbonbackbone and side chains represented by the formula—(O—CF₂CFR_(f))_(a)—O—CF₂CFR′_(f)SO₃Xwherein Rf and R′f are independently selected from F, Cl or aperfluorinated alkyl group having 1 to 10 carbon atoms, a=0, 1 or 2, andX is H, Li, Na, K or N(R1)(R2)(R3)(R4) and R1, R2, R3, and R4 are thesame or different and are and in one embodiment H, CH₃ or C₂H₅. Inanother embodiment X is H. As stated above, X may also be multivalent.

In one embodiment, the FSA polymers include, for example, polymersdisclosed in U.S. Pat. No. 3,282,875 and in U.S. Pat. Nos. 4,358,545 and4,940,525. An example of preferred FSA polymer comprises aperfluorocarbon backbone and the side chain represented by the formula—O—CF₂CF(CF₃)—O—CF₂CF₂SO₃Xwhere X is as defined above. FSA polymers of this type are disclosed inU.S. Pat. No. 3,282,875 and can be made by copolymerization oftetrafluoroethylene (TFE) and the perfluorinated vinyl etherCF₂═CF—O—CF₂CF(CF₃)—O—CF₂CF₂SO₂F,perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride) (PDMOF),followed by conversion to sulfonate groups by hydrolysis of the sulfonylfluoride groups and ion exchanged as necessary to convert them to thedesired ionic form. An example of a polymer of the type disclosed inU.S. Pat. Nos. 4,358,545 and 4,940,525 has the side chain —O—CF₂CF₂SO₃X,wherein X is as defined above. This polymer can be made bycopolymerization of tetrafluoroethylene (TFE) and the perfluorinatedvinyl ether CF₂═CF—O—CF₂CF₂SO₂F, perfluoro(3-oxa-4-pentenesulfonylfluoride) (POPF), followed by hydrolysis and further ion exchange asnecessary.

In one embodiment, the FSA polymers for use in this invention typicallyhave an ion exchange ratio of less than about 33. In this application,“ion exchange ratio” or “IXR” is defined as number of carbon atoms inthe polymer backbone in relation to the cation exchange groups. Withinthe range of less than about 33, IXR can be varied as desired for theparticular application. In one embodiment, the IXR is about 3 to about33, and in another embodiment about 8 to about 23.

The cation exchange capacity of a polymer is often expressed in terms ofequivalent weight (EW). For the purposes of this application, equivalentweight (EW) is defined to be the weight of the polymer in acid formrequired to neutralize one equivalent of sodium hydroxide. In the caseof a sulfonate polymer where the polymer has a perfluorocarbon backboneand the side chain is —O—CF₂—CF(CF₃)—O—CF₂—CF₂—SO₃H (or a salt thereof),the equivalent weight range which corresponds to an IXR of about 8 toabout 23 is about 750 EW to about 1500 EW. IXR for this polymer can berelated to equivalent weight using the formula: 50 IXR+344=EW. While thesame IXR range is used for sulfonate polymers disclosed in U.S. Pat.Nos. 4,358,545 and 4,940,525, e.g., the polymer having the side chain—O—CF₂CF₂SO₃H (or a salt thereof), the equivalent weight is somewhatlower because of the lower molecular weight of the monomer unitcontaining a cation exchange group. For the preferred IXR range of about8 to about 23, the corresponding equivalent weight range is about 575 EWto about 1325 EW. IXR for this polymer can be related to equivalentweight using the formula:50IXR+178=EW.

The FSA polymers can be prepared as colloidal aqueous dispersions. Theymay also be in the form of dispersions in other media, examples of whichinclude, but are not limited to, alcohol, water-soluble ethers, such astetrahydrofuran, mixtures of water-soluble ethers, and combinationsthereof. In making the dispersions, the polymer can be used in acidform. U.S. Pat. Nos. 4,433,082, 6,150,426 and WO 03/006537 disclosemethods for making of aqueous alcoholic dispersions. After thedispersion is made, concentration and the dispersing liquid compositioncan be adjusted by methods known in the art.

Aqueous dispersions of the colloid-forming polymeric acids, includingFSA polymers, typically have particle sizes as small as possible and anEW as small as possible, so long as a stable colloid is formed.

Aqueous dispersions of FSA polymer are available commercially as Nafion®dispersions, from E. I. du Pont de Nemours and Company (Wilmington,Del.).

In one embodiment, thiophene or the dioxythiophene monomers areoxidatively polymerized in water containing polymeric acid colloids.Typically, the thiophene or dioxythiophene monomers are combined with oradded to an aqueous dispersion containing a polymerization catalyst, anoxidizing agent, and colloidal polymeric acid particles dispersedtherein. In this embodiment, the order of combination or addition mayvary provided that the oxidizer and catalyst is not combined with themonomer until one is ready for the polymerization reaction to proceed.

Polymerization catalysts include, but are not limited to, ferricsulfate, ferric chloride, and the like and mixtures thereof.

Oxidizing agents include, but are not limited to, sodium persulfate,potassium persulfate, ammonium persulfate, and the like, includingcombinations thereof. The oxidative polymerization results in a stable,aqueous dispersion containing positively charged conductive polymericthiophene and/or dioxythiophene that is charged balanced by thenegatively charged side chains of the polymeric acids contained withinthe colloids, for example, sulfonate anion, carboxylate anion, acetylateanion, phosphonate anion, combinations, and the like.

In one embodiment of the method of making the aqueous dispersions ofpolydioxythiophene and at least one colloid-forming polymer acidinclude: (a) providing an aqueous dispersion of a polymer acid; (b)adding an oxidizer to the dispersion of step (a); (c) adding a catalystto the dispersion of step (b); and (d) adding a dioxythiophene monomerto the dispersion of step (c). One alternative embodiment to the abovedescribed method includes adding the dioxythiophene monomer to theaqueous dispersion of a polymeric acid prior to adding the oxidizer.Another embodiment, is to create a homogenous aqueous mixture of waterand the polydioxythiophene, of any number of polyoxythiopeneconcentrations in water which is typically in the range of about 0.5% byweight to about 2.0% by weight polyoxythiopene, and add thispolydioxythiophene mixture to the aqueous dispersion of the polymericacid before adding the oxidizer and catalyst.

The polymerization can be carried out in the presence of co-dispersingliquids which are miscible with water. Examples of suitableco-dispersing liquids include, but are not limited to ethers, alcohols,al ethers, cyclic ethers, ketones, nitriles, sulfoxides, andcombinations thereof. In one embodiment, the amount of co-dispersingliquid should be less than 30% by volume. In one embodiment, the amountof co-dispersing liquid is less than 60% by volume. In one embodiment,the amount of co-dispersing liquid is between 5% to 50% by volume. Inone embodiment, the co-dispersing liquid is an alcohol. In oneembodiment, the co-dispersing liquid is selected from n-propanol,isopropanol, t-butanol, methanol dimethylacetamide, dimethylformamide,N-methylpyrrolidone. The acid can be an inorganic acid, such as HCl,sulfuric acid, and the like, or an organic acid, such asp-toluenesulfonic acid, dodecylbenzenesulfonic acid, methanesulfonicacid, trifluoromethanesulfonic acid, camphorsulfonic acid, acetic acidand the like. Alternatively, the acid can be a water soluble polymericacid such as poly(styrenesulfonic acid),poly(2-acrylamido-2-methyl-1-propanesulfonic acid, or the like, or asecond colloid-forming acid, as described above. Combinations of acidscan be used.

The co-acid can be added to the reaction mixture at any point in theprocess prior to the addition of either the oxidizer or the thiophenemonomer, whichever is added last. In one embodiment, the co-acid isadded before both the thiophene monomer and the colloid-formingpolymeric acid, and the oxidizer is added last. In one embodiment theco-acid is added prior to the addition of the thiophene monomer,followed by the addition of the colloid-forming polymeric acid, and theoxidizer is added last.

The co-dispersing liquid can be added to the reaction mixture at anypoint prior to the addition of the oxidizer, catalyst, or monomer,whichever is last.

Optionally, after completion of any of the methods described above andcompletion of the polymerization reaction, the as-synthesized aqueousdispersion is contacted with at least one ion exchange resin underconditions suitable to produce a stable, aqueous dispersion. In oneembodiment, the as-synthesized aqueous dispersion is contacted with afirst ion exchange resin and a second ion exchange resin.

In another embodiment, the first ion exchange resin is an acidic, cationexchange resin, such as a sulfonic acid cation exchange resin set forthabove, and the second ion exchange resin is a basic, anion exchangeresin, such as a tertiary amine or a quaternary exchange resin.

Ion exchange is a reversible chemical reaction wherein an ion in a fluidmedium (such as an aqueous dispersion) is exchanged for a similarlycharged ion attached to an immobile solid particle that is insoluble inthe fluid medium. The term “ion exchange resin” is used herein to referto all such substances. The resin is rendered insoluble due to thecrosslinked nature of the polymeric support to which the ion exchanginggroups are attached. Ion exchange resins are classified as acidic,cation exchangers, which have positively charged mobile ions availablefor exchange, and basic, anion exchangers, whose exchangeable ions arenegatively charged.

Both acidic, cation exchange resins and basic, anion exchange resins arecontemplated for use in the practice of the invention. In oneembodiment, the acidic, cation exchange resin is an organic acid, cationexchange resin, such as a sulfonic acid cation exchange resin. Sulfonicacid cation exchange resins contemplated for use in the practice of theinvention include, for example, sulfonated styrene-divinylbenzenecopolymers, sulfonated crosslinked styrene polymers,phenol-formaldehyde-sulfonic acid resins, benzene-formaldehyde-sulfonicacid resins, and mixtures thereof. In another embodiment, the acidic,cation exchange resin is an organic acid, cation exchange resin, such ascarboxylic acid, acrylic or phosphoric acid cation exchange resin. Inaddition, mixtures of different cation exchange resins can be used. Inmany cases, the basic ion exchange resin can be used to adjust the pH tothe desired level. In some cases, the pH can be further adjusted with anaqueous basic solution such as a solution of sodium hydroxide, ammoniumhydroxide, tetra-methylammonium hydroxide, or the like.

In another embodiment, the basic, anionic exchange resin is a tertiaryamine anion exchange resin. Tertiary amine anion exchange resinscontemplated for use in the practice of the invention include, forexample, tertiary-aminated styrene-divinylbenzene copolymers,tertiary-aminated crosslinked styrene polymers, tertiary-aminatedphenol-formaldehyde resins, tertiary-aminated benzene-formaldehyderesins, and mixtures thereof. In a further embodiment, the basic,anionic exchange resin is a quaternary amine anion exchange resin, ormixtures of these and other exchange resins.

The first and second ion exchange resins may contact the as-synthesizedaqueous dispersion either simultaneously, or consecutively. For example,in one embodiment both resins are added simultaneously to anas-synthesized aqueous dispersion of an electrically conducting polymer,and allowed to remain in contact with the dispersion for at least about1 hour, e.g., about 2 hours to about 20 hours. The ion exchange resinscan then be removed from the dispersion by filtration. The size of thefilter is chosen so that the relatively large ion exchange resinparticles will be removed while the smaller dispersion particles willpass through. Without wishing to be bound by theory, it is believed thatthe ion exchange resins quench polymerization and effectively removeionic and non-ionic impurities and most of unreacted monomer from theas-synthesized aqueous dispersion. Moreover, the basic, anion exchangeand/or acidic, cation exchange resins renders the acidic sites morebasic, resulting in increased pH of the dispersion. In general, at least1 gram of ion exchange is used per about 1 gram of colloid-formingpolymeric acid. In other embodiments, the use of the ion exchange resinis used in a ratio of up to about 5 grams of ion exchange resin topolythiophene/polymeric acid colloid and depends on the pH that is to beachieved. In one embodiment, about one gram of Lewatit® MP62 WS, aweakly basic anion exchange resin from Bayer GmbH, and about one gram ofLewatit® MonoPlus S100, a strongly acidic, sodium cation exchange resinfrom Bayer, GmbH, are used per gram of the composition ofpolydioxythiophene and at least one colloid-forming polymeric acid.

In one embodiment, the aqueous dispersion resulting from polymerizationof dioxythiophene with fluorinated polymeric sulfonic acid colloids isto charge a reaction vessel first with an aqueous dispersion of thefluorinated polymer. To this is added, in order, the oxidizer, catalystand dioxythiophene monomer; or, in order, the dioxythiophene monomer,the oxidizer and catalyst. The mixture is stirred and the reaction isthen allowed to proceed at a controlled temperature. When polymerizationis completed, the reaction is quenched with a strong acid cation resinand a base anion exchange resin, stirred and filtered. Alternatively,the dioxythiophene can be added to water and stirred to homogenize themixture prior to addition of Nafion® dispersion, followed with oxidizingagent and catalyst. The oxidizer:monomer ratio is generally in the rangeof 0.5 to 2.0 The fluorinated polymer:dioxythiophene monomer ratio isgenerally in the range of 1 to 4. The overall solid content is generallyin the range of 1.5% to 6%; and in one embodiment 2% to 4.5%. Thereaction temperature is generally in the range of 5° C. to 50° C.; andin one embodiment 20° C. to 35° C. The reaction time is generally in therange of 1 to 30 hours.

As synthesized aqueous dispersions of polythiophenes polymer acidcolloids, including, polydioxythiophenes and fluorinated polymericsulfonic acid colloids, can have a wide range of pH and can be adjustedto typically be between about 1 to about 8, and generally have a pH ofabout 3-4. It is frequently desirable to have a higher pH, as theacidity can be corrosive. It has been found that the pH can be adjustedusing known techniques, for example, ion exchange or by titration withan aqueous basic solution. Stable dispersions of polydioxythiophenes andfluorinated polymeric sulfonic acid colloids with a pH up to 7-8 havebeen formed. Aqueous dispersions of polythiophenes and othercolloid-forming polymeric acids can be similarly treated to adjust thepH.

In another embodiment, more conductive dispersions are formed by theaddition of highly conductive additives to the aqueous dispersions ofpolydioxythiophene and the colloid-forming polymeric acid. Becausedispersions with relatively high pH can be formed, the conductiveadditives, especially metal additives, are not attacked by the acid inthe dispersion. Moreover, because the polymeric acids are colloidal innature, having the surfaces predominately containing acid groups,electrically conducting polythiophene is formed on the colloidalsurfaces. Because of this unique structure, only a low weight percentageof highly conductive additives, is needed to reach the percolationthreshold. Examples of suitable conductive additives include, but arenot limited to metal particles and nanoparticles, nanowires, carbonnanotubes, graphite fibers or particles, carbon particles, andcombinations thereof.

In another embodiment of the invention, there are provided buffer layerscast from aqueous dispersions comprising polythiophenes andcolloid-forming polymeric acids, including as one embodimentpolydioxythiophene and colloid-forming polymeric acids. In oneembodiment, the buffer layers are cast from aqueous dispersionscomprising colloid-forming polymeric sulfonic acid. In one embodiment,the buffer layer is cast from an aqueous dispersion containingpoly(alkylenedioxythiophene) and fluorinated polymeric acid colloids. Inanother embodiment, the fluorinated polymeric acid colloids arefluorinated polymeric sulfonic acid colloids. In still anotherembodiment, the buffer layer is cast from an aqueous dispersioncontaining poly(3,4-ethylenedioxythiophene) andperfluoroethylenesulfonic acid colloids.

The dried films of polythiophenes, including polydioxythiophenes, andpolymer acid colloids, such as fluorinated polymeric sulfonic acidcolloids are generally not redispersible in water. Thus the buffer layercan be applied as multiple thin layers. In addition, the buffer layercan be overcoated with a layer of different water-soluble orwater-dispersible material without being damaged.

In another embodiment, there are provided buffer layers cast fromaqueous dispersions comprising polythiophene, including polymericdioxythiophene, and colloid-forming polymeric acids blended with otherwater soluble or dispersible materials. Depending on the finalapplication of the material, examples of types of additional watersoluble or dispersible materials which can be added include, but are notlimited to polymers, dyes, coating aids, carbon nanotubes, nanowires,organic and inorganic conductive inks and pastes, charge transportmaterials, crosslinking agents, and combinations thereof. The materialscan be simple molecules or polymers. Examples of suitable other watersoluble or dispersible polymers include, but are not limited to,conductive polymers such as polythiophenes, polyanilines, polyamines,polypyrroles, polyacetylenes, and combinations thereof.

In another embodiment of the invention, there are provided electronicdevices comprising at least one electroactive layer (usually asemiconductor conjugated polymer) positioned between two electricalcontact layers, wherein at least one of the layers of the deviceincludes the buffer layer of the invention. One embodiment of thepresent invention is illustrated in one type of OLED device, as shown inFIG. 1, which is a device that has anode layer 110, a buffer layer 120,an electroluminescent layer 130, and a cathode layer 150. Adjacent tothe cathode layer 150 is an optional electron-injection/transport layer140. Between the buffer layer 120 and the cathode layer 150 (or optionalelectron injection/transport layer 140) is the electroluminescent layer130.

The device may include a support or substrate (not shown) that can beadjacent to the anode layer 110 or the cathode layer 150. Mostfrequently, the support is adjacent the anode layer 110. The support canbe flexible or rigid, organic or inorganic. Generally, glass or flexibleorganic films are used as a support. The anode layer 110 is an electrodethat is more efficient for injecting holes compared to the cathode layer150. The anode can include materials containing a metal, mixed metal,alloy, metal oxide or mixed oxide. Suitable materials include the mixedoxides of the Group 2 elements (i.e., Be, Mg, Ca, Sr, Ba, Ra), the Group11 elements, the elements in Groups 4, 5, and 6, and the Group 8-10transition elements. If the anode layer 110 is to be light transmitting,mixed oxides of Groups 12, 13 and 14 elements, such as indium-tin-oxide,may be used. As used herein, the phrase “mixed oxide” refers to oxideshaving two or more different cations selected from the Group 2 elementsor the Groups 12, 13, or 14 elements. Some non-limiting, specificexamples of materials for anode layer 110 include, but are not limitedto, indium-tin-oxide (“ITO”), aluminum-tin-oxide, gold, silver, copper,and nickel. The anode may also comprise an organic material such aspolyaniline or polypyrrole. The IUPAC number system is used throughout,where the groups from the Periodic Table are numbered from left to rightas 1-18 (CRC Handbook of Chemistry and Physics, 81^(st) Edition, 2000).

The anode layer 110 may be formed by a chemical or physical vapordeposition process or spin-cast process. Chemical vapor deposition maybe performed as a plasma-enhanced chemical vapor deposition (“PECVD”) ormetal organic chemical vapor deposition (“MOCVD”). Physical vapordeposition can include all forms of sputtering, including ion beamsputtering, as well as e-beam evaporation and resistance evaporation.Specific forms of physical vapor deposition include rf magnetronsputtering and inductively-coupled plasma physical vapor deposition(“IMP-PVD”). These deposition techniques are well known within thesemiconductor fabrication arts.

The anode layer 110 may be patterned during a lithographic operation.The pattern may vary as desired. The layers can be formed in a patternby, for example, positioning a patterned mask or resist on the firstflexible composite barrier structure prior to applying the firstelectrical contact layer material. Alternatively, the layers can beapplied as an overall layer (also called blanket deposit) andsubsequently patterned using, for example, a patterned resist layer andwet chemical or dry etching techniques. Other processes for patterningthat are well known in the art can also be used. When the electronicdevices are located within an array, the anode layer 110 typically isformed into substantially parallel strips having lengths that extend insubstantially the same direction.

The buffer layer 120 is usually cast onto substrates using a variety oftechniques well-known to those skilled in the art. Typical castingtechniques include, for example, solution casting, drop casting, curtaincasting, spin-coating, screen printing, inkjet printing, and the like.Alternatively, the buffer layer can be patterned using a number ofdepositing processes, such as ink jet printing.

The electroluminescent (EL) layer 130 may typically be a conjugatedpolymer, such as poly(paraphenylenevinylene), abbreviated as PPV, orpolyfluorene. The particular material chosen may depend on the specificapplication, potentials used during operation, or other factors. The ELlayer 130 containing the electroluminescent organic material can beapplied from solutions by any conventional technique, includingspin-coating, casting, and printing. The EL organic materials can beapplied directly by vapor deposition processes, depending upon thenature of the materials. In another embodiment, an EL polymer precursorcan be applied and then converted to the polymer, typically by heat orother source of external energy (e.g., visible light or UV radiation).

Optional layer 140 can function both to facilitate electroninjection/transport, and can also serve as a confinement layer toprevent quenching reactions at layer interfaces. More specifically,layer 140 may promote electron mobility and reduce the likelihood of aquenching reaction if layers 130 and 150 would otherwise be in directcontact. Examples of materials for optional layer 140 include, but arenot limited to, metal-chelated oxinoid compounds (e.g., Alq₃ or thelike); phenanthroline-based compounds (e.g.,2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (“DDPA”),4,7-diphenyl-1,10-phenanthroline (“DPA”), or the like); azole compounds(e.g., 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (“PBD” orthe like), 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole(“TAZ” or the like); other similar compounds; or any one or morecombinations thereof. Alternatively, optional layer 140 may be inorganicand comprise BaO, LiF, Li₂O, or the like.

The cathode layer 150 is an electrode that is particularly efficient forinjecting electrons or negative charge carriers. The cathode layer 150can be any metal or nonmetal having a lower work function than the firstelectrical contact layer (in this case, the anode layer 110). As usedherein, the term “lower work function” is intended to mean a materialhaving a work function no greater than about 4.4 eV. As used herein,“higher work function” is intended to mean a material having a workfunction of at least approximately 4.4 eV.

Materials for the cathode layer can be selected from alkali metals ofGroup 1 (e.g., Li, Na, K, Rb, Cs), the Group 2 metals (e.g., Mg, Ca, Ba,or the like), the Group 12 metals, the lanthanides (e.g., Ce, Sm, Eu, orthe like), and the actinides (e.g., Th, U, or the like). Materials suchas aluminum, indium, yttrium, and combinations thereof, may also beused. Specific non-limiting examples of materials for the cathode layer150 include, but are not limited to, barium, lithium, cerium, cesium,europium, rubidium, yttrium, magnesium, samarium, and alloys andcombinations thereof.

The cathode layer 150 is usually formed by a chemical or physical vapordeposition process. In general, the cathode layer will be patterned, asdiscussed above in reference to the anode layer 110. If the device lieswithin an array, the cathode layer 150 may be patterned intosubstantially parallel strips, where the lengths of the cathode layerstrips extend in substantially the same direction and substantiallyperpendicular to the lengths of the anode layer strips. Electronicelements called pixels are formed at the cross points (where an anodelayer strip intersects a cathode layer strip when the array is seen froma plan or top view).

In other embodiments, additional layer(s) may be present within organicelectronic devices. For example, a layer (not shown) between the bufferlayer 120 and the EL layer 130 may facilitate positive charge transport,band-gap matching of the layers, function as a protective layer, or thelike. Similarly, additional layers (not shown) between the EL layer 130and the cathode layer 150 may facilitate negative charge transport,band-gap matching between the layers, function as a protective layer, orthe like. Layers that are known in the art can be used. In addition, anyof the above-described layers can be made of two or more layers.Alternatively, some or all of inorganic anode layer 110, the bufferlayer 120, the EL layer 130, and cathode layer 150, may be surfacetreated to increase charge carrier transport efficiency. The choice ofmaterials for each of the component layers may be determined bybalancing the goals of providing a device with high device efficiencywith the cost of manufacturing, manufacturing complexities, orpotentially other factors.

The different layers may have any suitable thickness. Inorganic anodelayer 110 is usually no greater than approximately 500 nm, for example,approximately 10-200 nm; buffer layer 120, is usually no greater thanapproximately 250 nm, for example, approximately 50-200 nm; EL layer130, is usually no greater than approximately 1000 nm, for example,approximately 50-80 nm; optional layer 140 is usually no greater thanapproximately 100 nm, for example, approximately 20-80 nm; and cathodelayer 150 is usually no greater than approximately 100 nm, for example,approximately 1-50 nm. If the anode layer 110 or the cathode layer 150needs to transmit at least some light, the thickness of such layer maynot exceed approximately 100 nm.

Depending upon the application of the electronic device, the EL layer130 can be a light-emitting layer that is activated by signal (such asin a light-emitting diode) or a layer of material that responds toradiant energy and generates a signal with or without an appliedpotential (such as detectors or voltaic cells). After reading thisspecification, skilled artisans will be capable of selecting material(s)that are suitable for their particular applications. The light-emittingmaterials may be dispersed in a matrix of another material, with orwithout additives, and may form a layer alone. The EL layer 130generally has a thickness in the range of approximately 50-500 nm.

Examples of other organic electronic devices that may benefit fromhaving one or more layers comprising the aqueous dispersionpolythiophenes made with polymeric acid colloids include (1) devicesthat convert electrical energy into radiation (e.g., a light-emittingdiode, light emitting diode display, or diode laser), (2) devices thatdetect signals through electronics processes (e.g., photodetectors(e.g., photoconductive cells, photoresistors, photoswitches,phototransistors, phototubes), IR detectors), (3) devices that convertradiation into electrical energy, (e.g., a photovoltaic device or solarcell), and (4) devices that include one or more electronic componentsthat include one or more organic semi-conductor layers (e.g., atransistor or diode).

In organic light emitting diodes (OLEDs), electrons and holes, injectedfrom the cathode 150 and anode 110 layers, respectively, into the ELlayer 130, form negative and positively charged polar ions in thepolymer. These polar ions migrate under the influence of the appliedelectric field, forming a polar ion exciton with an oppositely chargedspecies and subsequently undergoing radiative recombination. Asufficient potential difference between the anode and cathode, usuallyless than approximately 12 volts, and in many instances no greater thanapproximately 5 volts, may be applied to the device. The actualpotential difference may depend on the use of the device in a largerelectronic component. In many embodiments, the anode layer 110 is biasedto a positive voltage and the cathode layer 150 is at substantiallyground potential or zero volts during the operation of the electronicdevice. A battery or other power source(s) may be electrically connectedto the electronic device as part of a circuit but is not illustrated inFIG. 1.

OLEDs provided with buffer layers cast from aqueous dispersionscomprising polymeric dioxythiophene and colloid-forming polymeric acidshave been found to have improved lifetimes. The buffer layer may be castfrom an aqueous dispersion of polydioxythiophene and fluorinatedpolymeric sulfonic acid colloids; an in one embodiment is an aqueousdispersion in which the pH has been adjusted to above about 3.5.

Using a less acidic or pH neutral material leads to significantly lessetching of the ITO layer during device fabrication and hence much lowerconcentration of In and Sn ions diffusing into the polymer layers of theOLED. Since In and Sn ions are suspected to contribute to reducedoperating lifetime this is a significant benefit.

The lower acidity also reduces corrosion of the metal components of thedisplay (e.g. electrical contact pads) during fabrication and over thelong-term storage. PEDT/PSSA residues will interact with residualmoisture to release acid into the displays with resulting slowcorrosion.

Equipment used to dispense the acidic PEDT/PSSA needs to be speciallydesigned to handle the strong acidity of PEDT/PSSA. For example, achrome-plated slot-die coating-head used to coat the PEDT/PSSA onto ITOsubstrates was found to be corroding due to the acidity of thePEDT/PSSA. This rendered the head unusable since the coated film becamecontaminated with particles of chrome. Also, certain ink-jet print headsare of interest for the fabrication of OLED displays. They are used fordispensing both the buffer layer and the light-emitting polymer layer inprecise locations on the display. These print-heads contain nickel meshfilters as an internal trap for particles in the ink. These nickelfilters are decomposed by the acidic PEDT/PSSA and rendered unusable.Neither of these corrosion problems will occur with the aqueous PEDTdispersions of the invention in which the acidity has been lowered.

Furthermore, certain light-emitting polymers are found to be sensitiveto acidic conditions, and their light-emitting capability is degraded ifthey are in contact with an acidic buffer layer. It is advantageous touse the aqueous PEDT dispersions of the invention to form the bufferlayer because of the lower acidity or neutrality.

The fabrication of full-color or area-color displays using two or moredifferent light-emitting materials becomes complicated if eachlight-emitting material requires a different cathode material tooptimize its performance. Display devices are made up of a multiplicityof pixels which emit light. In multicolor devices there are at least twodifferent types of pixels (sometimes referred to as sub-pixels) emittinglight of different colors. The sub-pixels are constructed with differentlight-emitting materials. It is very desirable to have a single cathodematerial that gives good device performance with all of the lightemitters. This minimizes the complexity of the device fabrication. Ithas been found that a common cathode can be used in multicolor deviceswhere the buffer layer is made from the aqueous PEDT dispersions of theinvention while maintaining good device performance for each of thecolors. The cathode can be made from any of the materials discussedabove; and may be barium, overcoated with a more inert metal such asaluminum.

Other organic electronic devices that may benefit from having one ormore layers comprising the aqueous dispersion of polythiophene,including polydioxythiophene, and at least one colloid-forming polymericacids include (1) devices that convert electrical energy into radiation(e.g., a light-emitting diode, light emitting diode display, or diodelaser), (2) devices that detect signals through electronics processes(e.g., photodetectors (e.g., photoconductive cells, photoresistors,photoswitches, phototransistors, phototubes), IR detectors), (3) devicesthat convert radiation into electrical energy, (e.g., a photovoltaicdevice or solar cell), and (4) devices that include one or moreelectronic components that include one or more organic semi-conductorlayers (e.g., a transistor or diode).

The buffer layer can further be overcoated with a layer of conductivepolymer applied from aqueous solution or solvent. The conductive polymercan facilitate charge transfer and also improve coatability. Examples ofsuitable conductive polymers include, but are not limited to,polyanilines, polythiophenes, polydioxythiophene/polystyrenesulfonicacid, polyaniline-polymeric-acid-colloids as disclosed in co-pendingapplication DuPont number UC 0223, polypyrroles, polyacetylenes, andcombinations thereof.

In yet another embodiment of the invention, there are provided thin filmfield effect transistors comprising electrodes comprisingpolydioxythiophenes and colloid-forming polymeric sulfonic acids. Foruse as electrodes in thin film field effect transistors, the conductingpolymers and the liquids for dispersing or dissolving the conductingpolymers must be compatible with the semiconducting polymers and thesolvents for the semiconducting polymers to avoid re-dissolution ofeither conducting polymers or semiconducting polymers. Thin film fieldeffect transistor electrodes fabricated from conducting polymers shouldhave a conductivity greater than 10 S/cm. However, electricallyconducting polymers made with water soluble polymeric acids only provideconductivity in the range of ˜10⁻³ S/cm or lower. Thus, in oneembodiment, the electrodes comprise poly(alkylenedioxythiophene) andfluorinated colloid-forming polymeric sulfonic acids in combination withelectrical conductivity enhancers such as nanowires, carbon nanotubes,or the like. In still another embodiment, the electrodes comprisepoly(3,4-ethylenedioxythiophene) and colloid-formingperfluoroethylenesulfonic acid in combination with electricalconductivity enhancers such as nanowires, carbon nanotubes, or the like.Invention compositions may be used in thin film field effect transistorsas gate electrodes, drain electrodes, or source electrodes.

Another illustration of the present invention, is the thin film fieldeffect transistors, is shown in FIG. 2. In this illustration, adielectric polymer or dielectric oxide thin film 210 has a gateelectrode 220 on one side and drain and source electrodes, 230 and 240,respectively, on the other side. Between the drain and source electrode,an organic semiconducting film 250 is deposited. Invention aqueousdispersions containing nanowires or carbon nanotubes are ideal for theapplications of gate, drain and source electrodes because of theircompatibility with organic based dielectric polymers and semiconductingpolymers in solution thin film deposition. Since the inventionconducting compositions, e.g., in one embodiment PEDT and colloidalperfluoroethylene sulfonic acid, exist as a colloidal dispersion, lessweight percentage of the conductive fillers is required (relative tocompositions containing water soluble polymeric sulfonic acids) to reachpercolation threshold for high electrical conductivity.

In still another embodiment of the invention, there are provided methodsfor producing, aqueous dispersions of polydioxythiophenes comprisingpolymerizing dioxythiophene monomers in the presence of polymericsulfonic acid colloids. In one embodiment of the invention methods, thepolydioxythiophene is a polyalkylenedioxythiophene and thecolloid-forming polymeric sulfonic acid is fluorinated. In anotherembodiment of the invention methods, the polydioxythiophene ispoly(3,4-ethylenedioxythiophene) and the colloid-forming polymericsulfonic acid is perfluorinated. In still another embodiment, thecolloid-forming polymeric sulfonic acid is perfluoroethylenesulfonicacid. The polymerization is carried out in the presence of water. Theresulting reaction mixture can be treated with ion exchange resins toremove reaction byproducts.

The invention will now be described in greater detail by reference tothe following non-limiting examples.

EXAMPLES Comparative Example 1

This Comparative Example demonstrates the oxidative polymerization ofethylenedioxythiophene in the presence of a water soluble, polymericsulfonic acid, i.e., poly(styrenesulfonic acid) (PSSA), to produce anon-colloidal poly(ethylenedioxythiophene)/poly(styrenesulfonic acid)(PEDT/PSSA) complex.

A solution of ferric sulfate was prepared by dissolving 0.3246 g offerric sulfate hydrate (Sigma-Aldrich Corp., St. Louis, Mo., USA) indeionized water to produce a solution with a total weight of 39.4566 g.2.28 g of this ferric sulfate solution was mixed in a plastic bottlewith 300 g of deionized water, 10.00 g of PSSA (30 wt % PSSA, 70,000molecular weight, PolySciences, Inc., Warmington, Pa., USA) and 1.72 gsodium persulfate (Fluka, Sigma-Aldrich Corp., St. Louis, Mo., USA). Theferric sulfate acts as a catalyst for the polymerization and the sodiumpersulfate is an oxidizing agent for the oxidative polymerization ofethylenedioxythiophene. The mixture was swirled and then placed in a3-necked 500 mL flask equipped with a thermal well for a thermocouple.The mixture was stirred with a stirring paddle powered by an air-drivenoverhead stirrer while 0.63 mL of 3,4-ethylenedioxythiophene (Baytron-M®obtained from Bayer, Pittsburgh, Pa., USA) was added to thePSSA-containing mixture. The polymerization of the3,4-ethylenedioxythiophene was allowed to proceed for 24 hours at roomtemperature, i.e., about 22° C. As a result of the polymerization, theclear liquid changed to a dark colored liquid, having the color of thePEDT/PSSA complex dispersed in water. The PEDT/PSSA complex dispersionwas tested for filterability with a 5.0 μm Millex®-SV syringe filterfrom Millipore Corp. (Bedford, Mass., USA). Only clear colorless liquidwent through the filter, with a high hand pressure exerted against thesyringe plunger, thereby indicating that the PEDT/PSSA complex particleswere too large to pass through the filter.

One half of the aqueous dispersion of the PEDT/PSSA complex, whichamounted to about 158 g, was further treated with two ion exchangeresins. One is a cation exchanger, sodium sulfonate of crosslinkedpolystyrene, (Lewatit® S100 WS, obtained from Bayer, Pittsburgh, Pa.,USA). The other is an anion exchanger, free base/chloride oftertiary/quaternary amine of crosslinked polystyrene, (Lewatit® MP62 WS,obtained from Bayer, Pittsburgh, Pa., USA). 53 g of Lewatit® S100 WS and51 g of Lewatit® MP62 WS were each washed with deionized water untilthere was no color in the water. The two washed resins were thenfiltered before being mixed with the 158 g of the aqueous dispersion ofthe PEDT/PSSA complex. The mixture was stirred with a magnetic stirrerfor 8 hours. The resins were removed by filtration. It was determinedthat the aqueous dispersion of the resin-treated PEDT/PSSA complexcontained 1.2 wt % solid based on a gravimetric analysis. The aqueousdispersion of the resin-treated PEDT/PSSA was then tested forfilterability with a 5.0 μm Millex®-SV syringe filter from MilliporeCorp. (Bedford, Mass., USA) and a 1.2 μm GF/C syringe filter fromWhatman Inc. (Clifton, N.J., USA). The dispersion passed through the 5.0μm Millex®-SV syringe filter, but only clear colorless liquid passedthrough the 1.2 μm GF/C syringe filter with a high hand pressure exertedagainst the syringe plunger. The average particle size of theresin-treated PEDT/PSSA complex particles was measured by lightscattering as described above and found to be 1.12 μm (average of fivemeasurements with standard deviation of 0.04 μm) with polydispersity of0.40.

The resin-treated PEDT/PSSA complex was then tested for electricalconductivity and light emission properties. Commercially availableindium tin oxide (ITO)/glass plates having ITO layers 100 to 150 nmthick were cut into samples 30 mm×30 mm in size. The ITO layers weresubsequently etched with oxygen plasma. The ITO on the glass substratesto be used for electrical conductivity measurements were etched into aseries of parallel lines of ITO to be used as electrodes. The ITO on thesubstrates to be made into LEDs for light emission measurement wereetched into a 15 mm×20 mm layer of ITO to serve as the anode. Theaqueous dispersion of the resin-treated PEDT/PSSA complex wasspin-coated onto each of the ITO/glass substrates at a spinning speed of1200 rpm. The resulting PEDT/PSSA complex layer was about 140 nm thick.The layer quality was not uniform. The PEDT/PSSA complex coatedITO/glass substrates were dried in nitrogen at 90° C. for 30 minutes.

Electrical conductivity of the PEDT/PSSA complex layer was determined bymeasuring the resistance between two electrodes and was calculated to be6.1×10⁻³ S/cm based on the resistance, the thickness of the conductivelayer and the distance between the two electrodes used to measure theresistance.

For light emission measurements, the PEDT/PSSA complex layer was thentop-coated with a super-yellow emitter poly(substituted-phenylenevinylene) (PDY 131 obtained from Covion Company, Frankfurt, Germany) toserve as the active electroluminescent (EL) layer. The thickness of theEL layer was approximately 70 nm. All film thicknesses were measuredwith a TENCOR 500 Surface Profiler. For the cathode, Ba and Al layerswere vapor deposited on top of the EL layer under a vacuum of 1.3×10⁻⁴Pa. The final thickness of the Ba layer was 3 nm; the thickness of theAl layer on top of the Ba layer was 300 nm. LED device performance wastested as follows. Measurements of current vs. applied voltage, lightemission intensity vs. applied voltage, and light emission efficiency(candela/ampere-c/A) were measured with a Keithley 236 source-measureunit from Keithley Instrument Inc. (Cleveland, Ohio), and a S370Optometer with a calibrated silicon photodiode (UDT Sensor, Inc.,Hawthorne, Calif.). Five LED devices were tested by raising the appliedvoltage to obtain a light intensity of 200 cd/m². The average appliedvoltage to achieve this intensity was 5.0 volts and the average lightefficiency was 5.4 cd/A. These devices had a stress half-life of lessthan one hour at 80° C.

Example 1

This Example illustrates polymerization of ethylenedioxythiophene in thepresence of Nafion® and also describes properties of thepoly(ethylenedioxythiophene) obtained thereby.

142.68 g (16.03 mmoles of Nafion® monomer units) SE-10072 and 173.45 gdeionized water were poured into a 500 mL Nalgenic® plastic bottle. Astock solution of ferric sulfate was made first by dissolving 0.0667 gferric sulfate hydrate (97%, Sigma-Aldrich Corp., St. Louis, Mo., USA)with deionized water to a total weight of 12.2775 g. 1.40 g of theferric sulfate solution and 1.72 g (7.224 mmoles) sodium persulfate(Fluka, Sigma-Aldrich Corp., St. Louis, Mo., USA) were then placed intothe plastic bottle. The cap of the Nalgenic® plastic bottle was replacedtightly and the bottle was the shaken vigorously by hand. The bottlecontents were poured into a jacketed 500 mL three-necked flask asdescribed above. The mixture was then stirred for 30 minutes in thereaction vessel. 0.63 mL (5.911 mmoles) of Baytron-M (a trade name for3,4-ethylenedioxythiophene from Bayer, Pittsburgh, USA) was added to thereaction mixture with stirring. Polymerization was allowed to proceedwith stirring at about 23° C. In one hour and 7 minutes, thepolymerization liquid turned very dark blue and was then distributedinto two 250 mL plastic bottles. When dismantling the reaction vessel,no gel particles were noticed on the stirring shaft or on the glass wallof the reaction vessel. Total yield of the polymerization liquid was297.10 g. The liquid contains 5.303% (w/w) solids assuming no loss andtotal conversion. The solid is presumed to contain primarilypoly(3,4-ethylenedioxythiophene), PEDT/Nafion®.

148.75 g of the aqueous PEDT/Nafion® in one of the two plastic bottleswas further treated with two ionic exchange resins. One of the tworesins is Lewatit® S100, a trade name from Bayer, Pittsburgh, Pa., USAfor sodium sulfonate of crosslinked polystyrene. The other ionicexchange resin is Lewatit® MP62 WS, a trade from Bayer, Pittsburgh, Pa.,USA for free base/chloride of tertiary/quaternary amine of crosslinkedpolystyrene. Before use, the two resins were washed with deionized waterseparately until there was no color observed in the water. 7.75 g ofLewatit® S100 and 7.8 g of Lewatit® MP62® WS were then mixed with the148.75 g aqueous PEDT/Nafion® dispersion in a plastic bottle. The bottlewas then placed on a roller for stirring for about 23 hours. Theresulting slurry was then suction-filtered through a coarsefritted-glass funnel. Yield was 110.2 g. Based on elemental analysis ofthe sample dried from a 2.6% (w/w) dispersion, the sample contains21.75% carbon, 0.23% hydrogen, 1.06% nitrogen and 2.45% sulfur. Otherelements such as oxygen and fluorine were not analyzed. To removefluorine interference with sulfur analysis, CeCl₃ and a cation exchangeresin was added.

10 g of the PEDT/Nafion® dispersion was mixed with 10.01 g deionizedwater, which constitutes 2.6% (w/w) solid based on a gravimetricanalysis of dried solid. The aqueous PEDT/Nafion® dispersion was thentested for conductivity and light emission properties. The glass/ITOsubstrates (30 mm×30 mm) having ITO thickness of 100 to 150 nm and 15mm×20 mm ITO area for light emission were cleaned and subsequentlytreated with oxygen plasma, as in Comparative Example 2. The aqueousPEDT/Nafion® dispersion was spin-coated onto the ITO/glass substrates ata spinning speed of 700 rpm to yield 96 nm thickness. The PEDT/Nafion®coated ITO/glass substrates were dried in a vacuum oven at 90° C. for 30minutes. Electrical conductivity of the PEDT/Nafion® films wasdetermined to be 2.4×10⁻³ and 5.7×10⁻⁴ S/cm. The PEDT/Nafion® layer wasthen top-coated with a super-yellow emitter (PDY 131), which is apoly(substituted-phenylene vinylene) from Covion Company (Frankfurt,Germany). The thickness of the EL layer was approximately 70 nm. Allfilm thicknesses were measured with a TENCOR 500 Surface Profiler. Forthe cathode, Ba and Al layers were vapor deposited on top of the ELlayers under a vacuum of 1×10⁻⁶ torr. The final thickness of the Balayer was 30 Å; the thickness of the Al layer was 3000 Å. Deviceperformance was tested as follows. Current vs. voltage, light emissionintensity vs. voltage, and efficiency were measured with a Keithley 236source-measure unit from Keithley Instrument Inc. (Cleveland, Ohio), anda S370 Optometer with a calibrated silicon photodiode from UDT Sensor,Inc. (Hawthorne, Calif.). Five light emitting devices tested showedoperating voltage ranging from 3.2 to 3.3 volts and light emissionefficiency ranging from 8.3 Cd/A to 9.8 Cd/A at 200 Cd/m² brightness.These devices have a stress half-life ranging from 243 to 303 hr at 80°C.

Comparative Example 2

This Comparative Example illustrates properties of solid films driedfrom a commercial aqueous PEDT dispersion made with water solublepoly(styrenesulfonic acid).

About 30 mL of Baytron-P VP AI 4083 (Lot#06Y76982) from H. C. Starck,GmbH (Leverkusen, Germany) was dried to solid films in a glass beakerunder a nitrogen flow at room temperature. The dried film flakes weremixed with about 10 mL deionized water and the mixture was shaken byhand. The water turned blue and became very dark as most of the flakeswere re-dispersed in the water. The water also became very acidic,having a pH of zero using a color pHast® Indicator (pH 0-14 range) fromEM Science (Gibbson, N.J., USA; cat#9590).

Comparative Example 3

This Comparative Example illustrates moisture uptake of solid filmsdried from another commercial aqueous PEDT dispersion made with watersoluble poly(styrenesulfonic acid):

About 30 mL of Baytron-P CH8000 (Lot# CHN0004) from H. C. Starck, GmbH(Leverkusen, Germany) was dried to solid films in a glass beaker under anitrogen flow at room temperature. A major portion of the dried filmswas tested for re-dispersibility and acidity in about 10 mL deionizedwater and found to behave as described in Comparative Example 2. A smallportion of the dried film flakes was then allowed to equilibrate atambient conditions before being analyzed for moisture uptake by athermal gravimetric analyzer (at 20° C./min in nitrogen). The filmflakes absorbed 29.4% water at ambient conditions. This result clearlydemonstrates that the PEDT films are very hygroscopic and, any moistureso absorbed the water would become very acidic as illustrated inComparative Example 2. Both VP AI 4083 and CH8000 PEDT are marketed forOLEDs as buffer layers.

Example 2

This Example illustrates properties of solid films dried from inventionaqueous PEDT/Nafion®.

About 30 mL of the aqueous PEDT/Nafion® (2.6%) in Example 1 was dried tosolid films in a glass beaker under a nitrogen flow at room temperature.A major portion of the dried film flakes was mixed with deionized waterand the mixture was shaken by hand. The flakes stayed shiny, indicatingthat the films were not swollen. Surprisingly, the water was colorless,meaning that PEDT/Nafion® was not re-dispersible in water. Moreover, thewater had a pH of 7 using a color pHast® Indicator (pH 0-14 range) fromEM Science (Gibbson, N.J., USA; cat#9590). This result clearly showsthat the polymeric acid is not mobile. Furthermore, the result showsthat the surface of the PEDT/Nafion® is predominantly a conductive layerhaving the sulfonic acid anions charge-balanced by the PEDT.

A small portion of the dried film flakes was allowed to equilibrate atambient conditions before being analyzed for moisture uptake by athermal gravimetric analyzer (at 20° C./min in nitrogen). The filmflakes absorbed only 5.6% water, which is far less than commercial PEDTas illustrated in Comparative Example 3. The low moisture uptake alsoshows that the surface of the PEDT/Nafion® is predominately a conductivelayer having the sulfonic acid anions charge-balanced by the PEDT. Thismakes it less hydroscopic than the dried films prepared in ComparativeExamples 2 and 3.

Example 3

This Example illustrates use of aqueous PEDT/Nafion® as electrodes inthin film field effect transistors.

A portion of the dried films described in Example 2 was mixed withtoluene, chloroform or dichloromethane (common organic solvents used fordissolving organic semiconducting polymers for use in thin film fieldeffect transistors). The film flakes were not swollen by either of theorganic solvents nor did the flakes discolor the solvents. This resultclearly demonstrates that PEDT/Nafion® films are compatible with organicsolvents for semiconducting polymers. Because the electricallyconducting polymers are cast from aqueous dispersions, the water willnot attack semiconducting polymers which are only soluble in organicaromatic solvents, such as toluene, or chlorinated solvents such aschloroform or dichloromethane.

The aqueous PEDT/Nafion® dispersion (2.6%, w/w) prepared in Example 2was tested for electrical conductivity. The glass/ITO substrates (30mm×30 mm) having ITO thickness of 100 to 150 nm were cleaned andsubsequently treated with oxygen plasma. The ITO substrates haveparallel-etched ITO lines on them for resistance measurement. Theaqueous PEDT/Nafion® dispersion was spin-coated onto the ITO/glasssubstrates. The PEDT/Nafion® coated ITO/glass substrates were dried in avacuum oven at 90° C. for 30 minutes. Electrical conductivity of thePEDT/Nafion® films was determined to be 2.4×10⁻³ and 5.7×10⁻⁴ S/cm. Theconductivity is lower than what is needed for thin film field effecttransistor electrodes. However, use of the conducting PEDT/Nafion® wherethe conducting polymers exist as colloids in the dispersion allows forincorporation of conductive fillers such as nano-wire, nanoparticles ofmetal, or carbon nanotubes. For example, metallic molybdenum wireshaving a diameter of 15 nm and a conductivity of 1.7×10⁻⁴ S/cm areavailable and can be used to enhance conductivity, as described in Zach,et al., Science, Vol. 290, p 2120. Carbon nanotubes having a diameter of8 nm, a length of 20 μm, and a conductivity of 60 S/cm are alsoavailable and can be used to enhance conductivity, as described in Niu,et al., Appl. Phys. Lett., Vol. 70, p. 1480. Because of the colloidalnature of the PEDT/Nafion® and because the surface of the particles ispredominately an electrically conductive layer, a lower weightpercentage of the highly conductive fillers is needed to reachpercolation threshold for high conductivity once the PEDT/Nafion®coalesces.

Example 4

This Example illustrates the polymerization of ethylendioxythiophene inthe presence of Nafion® under varying conditions. Three different typesof Nafion® resin were used: SE-10072, DE-1021, and DE-1020.

To a jacketed flask were added an aqueous Nafion® dispersion and water.The mixture was warmed to the temperature indicated and stirred for 45minutes. To this mixture were added, in order, the oxidizer, catalystand dioxythiophene monomer. After the addition was complete, the mixturewas allowed to stir at the temperature indicated, for the timeindicated. The reaction was then quenched with Lewatit® strong acidcation resin (sodium form) and Lewatit® weak base anion resin, either bybatch treatment of the reaction mixture, or by passing through a columnfilled with these two ion exchange resins. The resulting slurry mixturewas then stirred for 16 hours at room temperature and then filteredthrough filter paper (pore size >20-25 micrometer). The filtrate wasthen filtered through filter paper (pore size >6 micrometer). Finally,the filtrate obtained was filtered through a 0.45 micrometer filter. Theresulting filtrate was formulated to a final product with the targetsolid content by adding DI was and mixed well by shaking. Thepolymerization parameters are summarized in Table 1 below.

TABLE 1 Summary of Synthesis of PEDT/Nafion ® As is Formulated NafionOxidizer/ Nafion/ Temp. Reaction Ion PEDT.Nafion PEDT.Nafion SampleBatch Monomer Monomer (° C.) Time (hr, min) Exchange (%) (%) A SE- 1.2212.756 20.2 20, 49 Batch 2.81 2.8 10072 B DE-1021 1.221 2.756 20.2 20, 47Batch 2.81 2.8 C DE-1021 1.221 2.756 20.2 21, 00 Column 2.81 2.8 DDE-1020 1.221 2.756 20.2 21, 00 Batch 2.81 2.8 E DE-1020 1.221 2.75620.1 21, 00 Column 2.81 2.8 F DE-1020 1.221 5.513 20.2 23, 15 Column2.80 5.5 G DE-1021 1.221 5.513 20.2 44, 08 Column 2.80 5.9 H DE-10201.221 5.513 20.2 24, 56 Batch 5.48 5.4 I DE-1020 0.50 3.00 20.2 23, 43Batch 2.89 2.8 J DE-1020 1.50 3.00 20.1 24, 00 Column 2.69 2.6 K DE-10202.00 1.00 20.1 14, 52 Batch 3.04 3.0 L DE-1020 1.25 3.00 35.0 16, 34Batch 6.04 3.4 M DE-1020 2.00 3.00 35.0 24, 05 Column 3.01 3.0 N DE-10201.25 3.00 35.0 14, 54 Batch 4.52 3.4 O DE-1020 1.5 3.00 35.0 14, 55Batch 4.52 4.5 P DE-1020 0.75 3.00 35.0 24, 00 Batch 4.51 4.5 Q DE-10201.00 3.00 35.0 16, 36 Batch 4.52 3.8 R DE-1020 1.00 2.00 35.0 16, 31Batch 4.52 4.5 S DE-1020 1.00 2.50 35.0 16, 28 Batch 4.52 3.0 T DE-10201.00 3.00 35.0 41, 17 Batch 3.51 3.5 U DE-1020 1.25 3.00 35.0 41, 19Batch 3.51 3.5 V DE-1020 1.50 3.00 35.0 41, 22 Batch 3.51 3.5 W DE-10201.25 3.00 35.0 14, 02 Column 4.52 3.0 X DE-1020 1.00 2.75 35.0 14, 27Batch 4.52 3.6 Y DE-1020 1.00 2.25 35.0 13, 20 Batch 4.52 3.6 Z DE-10201.25 2.75 35.0 14, 28 Batch 4.52 3.6 AA DE-1020 1.25 2.50 35.0 13, 47Batch 4.52 3.5 BB DE-1020 1.25 2.25 35.0 13, 39 Batch 4.53 3.5 CCDE-1020 1.25 2.00 35.0 13, 42 Batch 4.53 3.5 DD DE-1020 1.50 2.75 35.013, 16 Batch 4.53 3.5 EE DE-1020 1.50 2.50 35.0 13, 17 Batch 4.53 3.5 FFDE-1020 1.50 2.25 35.0 13, 18 Batch 4.53 2.8 GG DE-1020 1.50 2.00 35.012, 58 Batch 4.54 3.0 HH DE-1020 1.75 3.00 35.0 13, 10 Batch 4.53 3.5 IIDE-1020 1.75 2.75 35.0 13, 05 Batch 4.53 3.0 JJ DE-1020 0.75 2.75 35.013, 27 Batch 4.51 3.5 KK DE-1020 0.75 2.50 35.0 13, 25 Batch 4.51 3.5 LLDE-1020 0.75 2.25 35.0  5, 55 Batch 4.52 3.5 MM DE-1020 0.75 2.00 35.0 5, 52 Batch 4.52 3.0 NN DE-1020 0.50 3.00 35.0 23, 38 Batch 4.51 3.5 OODE-1020 0.50 2.75 35.0 23, 38 Batch 4.51 3.5 PP DE-1020 0.50 2.50 35.022, 53 Batch 4.51 3.5 QQ DE-1020 0.50 2.25 35.0 22, 54 Batch 4.51 3.5

Example 5

This Example illustrates the difference in conductivity in filmsprepared from the PEDT/Nafion® dispersions from Example 4. Glasssubstrates were prepared with patterned ITO electrodes. Buffer layerswere spin cast from the dispersions indicated to form films on top ofthe patterned substrates, and thereafter baked at 90° C. in a vacuumoven for 0.5 hours. The resistance between ITO electrodes was measuredusing a high resistance electrometer in dry box. Thickness of the filmwas measured by using a Dec-Tac surface profiler (Alpha-Step 500 SurfaceProfiler, Tencor Instruments). The conductivity of buffer layer iscalculated from the resistance and thickness.

The results are shown graphically in FIGS. 3 and 4. It can be seen thatthe conductivity could be well controlled in the range of 10⁻² S⊙cm⁻¹ to10⁻⁹ S⊙cm⁻¹ by varying the composition.

Example 6

This Example illustrates the performance of different PEDT/Nafion®compositions used as buffer layers in OLEDs.

Light emitting diodes were fabricated using solublepoly(1,4-phenylenevinylene) copolymer (C-PPV) (H. Becker, H. Spreitzer,W. Kreduer, E. Kluge, H. Schenk, I.D. Parker and Y. Cao, Adv. Mater. 12,42 (2000)) as the active semiconducting, luminescent polymer; thethickness of the C-PPV films were 700-900 Å. C-PPV emits yellow-greenlight with emission peak at ˜560 nm. Indium/tin oxide was used as theanode. PEDT/Nafion® films were spin-cast on top of the patternedsubstrates from solutions, and thereafter, baked at 90° C. in a vacuumoven for 0.5 hour. The device architecture wasITO/PEDT-Nafion®/C-PPV/metal. Devices were fabricated using ITO on glassas the substrate (Applied ITO/glass). Devices were made with a layer ofeither Ca or Ba as the cathode. The metal cathode film was fabricated ontop of the C-PPV layer using vacuum vapor deposition at pressures below1×10⁻⁶ Torr yielding an active layer with area of 3 cm². The depositionwas monitored with a STM-100 thickness/rate meter (Sycon Instruments,Inc.). 2,000-5,000 Å of aluminum was deposited on top of the 30 Å ofbarium or calcium layer. For each of the devices, the current vs.voltage curve, the light vs. voltage curve, and the quantum efficiencywere measured.

The devices were encapsulated using a cover glass sandwiched byUV-curable epoxy. The encapsulated devices were run at a constantcurrent in an oven at 80° C. The total current through the device was˜10 mA with luminance of approx. 200 cd/m² or 600 cd/m². The luminanceand voltage of the devices were recorded to determine the half life timeand voltage increase rate at 80° C.

The results are given in Table 2 below.

TABLE 2 Device Performance Spin at 80° C. Sample Rate Thick.Conductivity Volt. Eff. I.L. t_(1/2) ID [rpm] [Å] [S/cm] [V] [cd/A][cd/m2] [h] I.L * t½ 4-N 3000 1114 1.2 × 10−6 3.8-3.9 (1) 7.8-8.8 (1)141 252 35532 4-Q 2000 2096 6.9 × 10−5 3.0-3.1 (1) 8.8-9.7 (1) 162 31751354 4-X 2300 1390 1.0 × 10−4 3.5 (2) 10.6 (2) 468 140 65520 4-Z 2000840 5.9 × 10−6 4.6 (2)  9.3 (2) 471 102 48042 4-AA 800 1227 2.4 × 10−5 4(2) 10 (2) 449 112 50288 Comp. 1 1200 1400 6.1 × 10−3 5 (1)  5.4 (1) <1I.L. = initial luminance (1) measured at 200 cd/m2 (2) measured at 600cd/m2

Example 7

This Example illustrates the preparation of an aqueous dispersion ofPEDT/Nafion®. The Nafion® was a 12.5% (w/w) aqueous colloidal dispersionwith an EW of 990, made using a procedure similar to the procedure inU.S. Pat. No. 6,150,426, Example 9.

63.87 g (8.06 mmoles of Nafion® monomer units) Nafion® aqueous colloidaldispersion, and 234.47 g deionized water was massed into a 500 mLjacketed three-necked round bottom flask. The mixture was stirred for 45minutes before the addition of ferric sulfate and sodium persulfate. Astock solution of ferric sulfate was made first by dissolving 0.0141 gferric sulfate hydrate (97%, Aldrich cat. #30, 771-8) with deionizedwater to a total weight of 3.6363 g. 0.96 g (0.0072 mmoles) of theferric sulfate solution and 0.85 g (3.57 mmoles) sodium persulfate(Fluka, cat. #71899) were then placed into the reaction flask while themixture was being stirred. The mixture was then stirred for 3 minutesprior to addition of 0.312 mL (2.928 mmoles) of Baytron-M (a trade namefor 3,4-ethyylenedioxythiophene from Bayer, Pittsburgh, USA) was addedto the reaction mixture while stirring. The polymerization was allowedto proceed with stirring at about 20° C. controlled by circulationfluid. The polymerization liquid started to turn blue in 13 minutes. Thereaction was terminated in 16.1 hours by adding 8.91 g Lewatit® S100, atrade name from Bayer, Pittsburgh, Pa., for sodium sulfonate ofcrosslinked polystyrene, and 7.70 g Lewatit® MP62 WS, a trade fromBayer, Pittsburgh, Pa., for free base/chloride of tertiary/quaternaryamine of crosslinked polystyrene. The two resins were washed firstbefore use with deionized water separately until there was no color inthe water. The resin treatment proceeded for 5 hrs. The resulting slurrywas then suction-filtered through a Whatman #54 filter paper. It wentthrough the filter paper very fast. Yield was 244 g. Solid % was about3.1% (w/w) based on added polymerization ingredients. pH of the aqueousPEDT/Nafion® was determined to be 3.8 with a 315 pH/Ion meter fromCorning Company (Corning, N.Y., USA).

Example 8

This example illustrates the non-dispersibility of dried films ofPEDT/Nafion®.

About 10 mL of the aqueous PEDT/Nafion® dispersion prepared in Example 7was dried with a nitrogen stream at ambient temperature. The driedPEDT/Nafion® was mixed with 10 mL deionized water. The water remainedcolorless and clear for many months.

Example 9

This example illustrates the non-corrosiveness of the aqueousPEDT/Nafion® dispersion to ITO.

The aqueous PEDT/Nafion® prepared in Example 7 was used to spin-coat onan ITO substrate. The PEDT/Nafion® top surface was examined using X-rayphotoelectron spectroscopy (XPS). There was no indium or tin elementdetected, indicating that the ITO was not attacked by the aqueousPEDT/Nafion® dispersion, which had a pH of 3.8.

Comparative Example 4

This comparative example illustrates the re-dispersibility of driedBaytron-P and its corrosiveness to ITO.

CH8000, one of the OLED grades of Baytron-P from H. C. Starck, GmbH(Leverkusen, Germany), is an aqueous poly(3,4-dioxyethylenethiophene),PEDT, made with polystyrenesulfonic acid (PSSA). The ratio of PEDT toPSSA and polystyrenesulfonate (PSS) is 1:20 (w/w). PEDT/PSS/PSSA has apH in the range of 1. PEDT/PSS/PSSA dried at ambient conditions from theaqueous dispersion re-dispersed in water very readily. The PEDT/PSS/PSSAwas coated onto ITO as in Example 9. The top surface was examined usingX-ray photoelectron spectroscopy (XPS). Both indium and tin elementswere detected, indicating that ITO was attacked by the aqueousPEDT/PSSA/PSS dispersion, which had a pH of ˜1.

Examples 10-12

These examples illustrate the use of PEDT/Nafion® in multilayercoatings.

Example 10

This example illustrates the formation of thicker layers by usingmultiple layer coatings of aqueous PEDT/Nafion®.

An aqueous PEDT/Nafion® dispersion prepared in an identical manner as inExample 7, was spin-coated three times consecutively at a spin speed of800 rpm. Between each spin coating, the cast film was baked at 90° C. invacuo. Thickness was taken with a Tencor profilometer, average of twomeasurements.

1st layer=99 nm after bake.

2nd layer (total thickness)=203 nm after bake.

3rd layer (total thickness)=322 nm after bake.

The thickness data clearly illustrates that each deposition has athickness of about 100 nm. Moreover, the data also shows that driedPEDT/Nafion® films are not re-dispersible in water.

Example 11

This example illustrates the use of PEDT/Nafion® in an OLED with twobuffer layers, where the PEDT/Nafion® is in contact with the ITO anode.

Two aqueous PEDT dispersions were used for construction of double bufferlayers for light emission tests. One is CH8000 (lot # KIM4952) describedin Comparative Example 4. The other is aqueous PEDT/Nafion® described inExample 7. The glass/ITO substrates (30 mm×30 mm) having ITO thicknessof 100 to 150 nm and 15 mm×20 mm ITO area for light emission werecleaned and subsequently treated with oxygen plasma. The aqueousPEDT/Nafion® dispersion was spin-coated onto the ITO/glass substratesfirst and subsequently baked at 90° C. for 30 minutes in vacuo. ThePEDT/Nafion® layer was then top-coated with CH8000 and subsequentlybaked at 90° C. for 30 minutes in vacuo. The total thickness of doublelayers is 86 nm. The double buffer layers were then top-coated with axylene solution (1.2% w/w) of BP-79 (Dow Chemical, blue light emittingpolymer). Thickness of the BP-79 layer is 70 nm. The BP-79 layer wasthen vapor-deposited with LiF, Ca and finally aluminum under a vacuum of1×10⁻⁶ torr with respective thickness of 2 nm, 20 nm and 500 nm. Thedevices made from the double layer construction have an initialefficiency of 2.9 to 3.5 Cd/A and initial operating voltage of 3.8 to3.9 volt. Half-life of the devices at room temperature is 307 hours.

This illustrates the utility of PEDT/Nafion® as a passivation layer forITO.

Example 12

This Example illustrates the use of PEDT/Nafion® in an OLED with twobuffer layers, where the PEDT/Nafion® is in contact with the EL layer.

CH8000 (lot# KIM4952) was spin-coated onto the ITO/glass substratesdescribed in Example 11, and subsequently baked at 200° C. for 3 minuteson hotplate in air. The thickness of the layer was 85 nm. The CH8000layer was then top-coated with the aqueous PEDT/Nafion® and subsequentlybaked at 90° C. for 30 minutes in vacuo. The thickness of thePEDT/Nafion® layer was 21 nm. The double buffer layers were thentop-coated with a xylene solution (1.2% w/w) of BP-79 (Dow Chemical,blue light emitting polymer). The thickness of the BP-79 layer was 70nm. The BP-79 layer was then vapor-deposited with LiF, Ca and finallyaluminum under a vacuum of 1×10⁻⁶ torr with respective thicknesses of 2nm, 20 nm and 500 nm. The devices made from the double layerconstruction had an initial efficiency of 2.5 to 3.1 Cd/A and an initialoperating voltage of 4.1 to 4.2 volt. The half-life of the devices atroom temperature was 54 hours. This is similar to the lifetime ofdevices made with CH8000 alone and much less than the half-lifedescribed in Example 11. The comparison illustrates the passivationfunction of PEDT/Nafion® in contact with the ITO substrates.

Example 13

This Example illustrates the improved operating lifetime of OLED devicesusing a PEDT/Nafion® buffer layer and a green light-emitting polymer.

OLED devices were fabricated as follows: 30 mm×30 mm glass substrateshaving a 15 mm×20 mm ITO area were cleaned with solvents and oxygenplasma. The ITO layer was 100-150 nm thick. The aqueous PEDT/Nafion®dispersion was spin-coated, in air, onto the ITO/glass substrates andbaked at 90° C. for 30 minutes in vacuum. The dried film thickness wasin the range 50-100 nm. These substrates were then transferred into anitrogen filled dry box with oxygen and water levels ˜1 ppm. Thelight-emitting polymer, DOW Green K2 (Dow Chemical Co., Midland, Mich.),was spin-coated on top of the PEDT/Nafion® layer. The DOW K2 solutionwas ˜1% solids in a xylene solvent. The films were then baked a secondtime at 130° C. for 5 minutes in the dry-box. Thickness of the K2 layerwas ˜75 nm. These substrates were then transferred into a thermalevaporator and cathode deposited under a vacuum of approx. 1×10−6 torr.The cathode consisted of ˜5 nm Ba followed by ˜0.5 micron of Al. Finallythese devices were removed from the dry-box and hermetically sealedprior to operational lifetime testing in an environmental chamber. Theoperating-lifetime testing conditions for these displays were: Initialluminance 200 cd/m2, DC constant current, testing temperature of 80° C.(in order to accelerate the testing process).

The results are shown graphically in FIG. 5. The estimated lifetime forthe displays with PEDT/Nafion® was approximately 10× longer than for thedisplay with PEDT/PSSA. The initial operating voltage was ˜10% lower forPEDT/Nafion®. In addition, the voltage increase rate was ˜25% lower.

Example 14

This Example illustrates the improved operating lifetime of OLED devicesusing a PEDT/Nafion® buffer layer and a red light-emitting polymer.

OLED devices were fabricated as follows: 30 mm×30 mm glass substrateshaving a 15 mm×20 mm ITO area were cleaned with solvents and oxygenplasma. The ITO layer is 100-150 nm thick. The aqueous PEDT/Nafion®dispersion was spin-coated, in air, onto the ITO/glass substrates andbaked at 90° C. for 30 minutes in vacuum. The dried film thickness wasin the range 50-100 nm. These substrates were then transferred into anitrogen filled dry box with oxygen and water levels ˜1 ppm. Thelight-emitting polymer, AEF 2157 (Covion GmbH, Frankfurt, Germany), wasspin-coated on top of the PEDT/Nafion® layer. The AEF 2157 solution was˜1% solids in a toluene solvent. The films were then baked a second timeat 130° C. for 5 minutes in the dry-box. Thickness of the AEF 2157 layerwas ˜75 nm. These substrates were then transferred into a thermalevaporator and cathode deposited under a vacuum of approx. 1×10-6 torr.The cathode consisted of ˜5 nm Ba followed by ˜0.5 micron of Al. Finallythese devices were removed from the dry-box and hermetically sealedprior to operational lifetime testing in an environmental chamber. Theoperating lifetime testing conditions for these displays were: Initialluminance 170 cd/m2, DC constant current, testing temperature of 80° C.(in order to accelerate the testing process).

The results are shown graphically in FIG. 6. The estimated lifetime forthe displays with PEDT/Nafion® was approximately 4× longer than for thedisplay with PEDT/PSSA. The initial operating voltage was ˜20% lower forPEDT/Nafion®. Also, the voltage increase rate was >3× lower.

Example 15

This Example illustrates the improved operating lifetime of OLED devicesusing a PEDT/Nafion® buffer layer and a blue light-emitting polymer.

OLED devices were fabricated as follows: 30 mm×30 mm glass substrateshaving a 15 mm×20 mm ITO area were cleaned with solvents and oxygenplasma. The ITO layer is 100-150 nm thick. The aqueous PEDT/Nafion®dispersion was spin-coated, in air, onto the ITO/glass substrates andbaked at 90° C. for 30 minutes in vacuum. The dried film thickness wasin the range 50-100 nm. These substrates were then transferred into anitrogen filled dry box with oxygen and water levels ˜1 ppm. Thelight-emitting polymer, SCB-11 (Dow Chemical Co., Midland, Mich.), wasspin-coated on top of the PEDT/Nafion® layer. The SCB-11 solution was˜1% solids in a xylene solvent. The films were then baked a second timeat 130° C. for 5 minutes in the dry-box. Thickness of the SCB-11 layerwas ˜75 nm. These substrates were then transferred into a thermalevaporator and cathode deposited under a vacuum of approx. 1×10⁻⁶ torr.The cathode consisted of ˜2 nm LiF, followed by 20 nm of Ca, and then˜0.5 micron of Al. Finally these devices were removed from the dry-boxand hermetically sealed prior to operational lifetime testing in anenvironmental chamber. The operating lifetime testing conditions forthese displays were: Initial luminance 170 cd/m2, DC constant current,testing temperature of 80° C. (in order to accelerate the testingprocess).

The results are shown graphically in FIG. 7. The estimated lifetime forthe displays with PEDT/Nafion® was approximately 10× longer than for thedisplay with PEDT/PSSA. The initial operating voltage was ˜20% lower forPEDT/Nafion®. Also, the voltage increase rate was more than 6× lower.

Examples 16-21

These Examples illustrate the effect of pH on different PEDT bufferlayers.

Example 16

This Example illustrates the preparation of PEDT/Nafion®. The Nafion®was a 12.5% (w/w) aqueous colloidal dispersion with an EW of 1050, madeusing a procedure similar to the procedure in U.S. Pat. No. 6,150,426,Example 9.

150.90 g (17.25 mmoles of Nafion® monomer units) Nafion® (1050 EW)aqueous colloidal dispersion (12.%, w/w) and 235.11 g deionized waterwas massed into a 500 mL Nalgene® plastic bottle, which was then rolledfor about two hours. The diluted colloidal dispersion was thentransferred to a 500 mL jacketed three-necked round bottom flask. Due toa small loss of the dispersion in the transfer, only 146.18 g Nafion®was transferred, which amounted to 16.71 mmoles Nafion® in the reactionflask. A stock solution of ferric sulfate was made first by dissolving0.0339 g ferric sulfate hydrate (97%, Aldrich cat. #30, 771-8) withdeionized water to a total weight of 3.285 g. 1.50 g (0.0315 mmoles) ofthe ferric sulfate solution and 1.76 g (7.392 mmoles) sodium persulfate(Fluka, cat. #71899) were then placed into the reaction flask while themixture was being stirred. The mixture was then stirred for 5 minutesprior to addition of 0.647 mL (6.071 mmoles) of Baytron-M whilestirring. The polymerization was allowed to proceed with stirring atabout 20° C. controlled by circulation fluid. The polymerization liquidstarted to turn blue in 5 minutes. The reaction was terminated in 3.2hours by adding 20.99 g Lewatit® S100 and 20.44 g Lewatit® MP62 WS, asin Example 7. The two resins were washed first before use with deionizedwater separately until there was no color in the water. The resintreatment was preceded for 21 hrs. The resulting slurry was thensuction-filtered through a Whatman #54 filter paper. Filtration wasfairly easy. Solid % was about 4.89% (w/w) based on added polymerizationingredients.

255.6 g of the PEDT/Nafion® was added with deionized water to a totalweight of 480.8 g, to make 2.6% solid (w/w). The pH of the dilutedaqueous PEDT/Nafion® was determined to be 3.9 with a 315 pH/Ion meterfrom Corning Company (Corning, N.Y., USA).

Example 17

This example illustrates the preparation of a PEDT/Nafion® dispersionwith a pH of 2.2.

The diluted PEDT/Nafion® prepared in Example 16 was used as a startingmaterial. 3.07 g Dowex 550A resin (Aldrich Cat. #43, 660-7), a strongbase anion exchange resin, was added and left stirring for 1.2 hrs. TheDowex 550A was washed first before use with deionized water until therewas no color in the water. The mixture was filtered and the filtrate wasadded with 3.0 g Amberlyst 15 (Aldrich Cat #21,639,9, proton cationexchange resin.) and left stirred for 45 minutes and filtered. Thefiltrate was added with 3.0 g of fresh Amberlyst 15 and left stirred 15hours and filtered for OLED testing. Amberlyst 15 was washed firstbefore use with deionized water several times. The pH of Amberlyst 15treated aqueous PEDT/Nafion® was determined to be 2.2.

Example 18

This example illustrates the preparation of a PEDT/Nafion® dispersionwith a pH of 4.3

A batch of PEDT/Nafion® was prepared in the same manner as in Example16. 61.02 g of the as-prepared dispersion was diluted to 2.8% (w/w) with45.05 g deionized water. The diluted dispersion had a pH of 4.3.

Example 19

This example illustrates the preparation of a PEDT/Nafion® dispersionwith a pH of 7.0 using lithium salts.

A dispersion of PEDT/Nafion®, neutralized with lithium ions is describedbelow. This is a two step process: first residual metal ions left overfrom the synthesis are removed by exchanging them with protons; then asecond ion exchange is used to exchange these protons with lithium ions.This gives a dispersion of high purity.

The diluted PEDT/Nafion® as described in Example 16 was first treatedwith 5.13 g Dowex 550A resin (Aldrich Cat. #43, 660-7), a strong baseanion exchange resin, and left stirring for 2 hrs. The Dowex 550A waswashed first before use with deionized water until there was no color inthe water. The mixture was filtered and the filtrate was treated with4.13 g Amberlyst 15 (Aldrich Cat #21,639,9, proton cation exchangeresin.) and left stirring for 10 hrs and filtered. Then 3.14 g of freshAmberlyst 15 was added and left stirring for 1.5 hrs. Finally thedispersion was filtered.

37.82 g of the acidified PEDT/Nafion® was then treated with 1.99 g, 2.33g, 2.06 g, 2.08 g and 2.00 g lithium salt of Amberlyst 15. Betweenreplacements of each fresh lithium salt of Amberlyst 15, the mixture wasfiltered. Also, the mixture was stirred between each filtration and thetotal resin treatment time was 7 hours. The pH of the treated Nafion®was determined to be 7.0.

Example 20

This example illustrates the preparation of a PEDT/Nafion® dispersionwith a pH of 7.2 using Sodium salts.

A dispersion of PEDT/Nafion®, neutralized with sodium ions is described.The starting material is the lithium ion dispersion described in example16. Further treatment exchanges the lithium ions for sodium ions asdescribed below. This gives a dispersion of high purity.

The diluted PEDT Nafion® as described in Example 16 was first treatedwith 2.76 g, 3.57 g, 3.55 g, and 3.25 g Lewatit® S100. Betweenreplacement of each fresh resin, the mixture was filtered. Also, themixture was stirred between each filtration and the total resintreatment time was 7 hours. The pH of the treated Nafion® was determinedto be 7.2.

Comparative Example 5

This Comparative Example illustrates the preparation of PEDT/PSSAdispersions with modified pH values.

Sample Comp. 5-A

PEDT/PSSA (AI4083, an OLED grade of Baytron-P from H. C. Starck GmbHLeverkusen, Germany) has a pH of 1.8.

Sample Comp. 5-B

58.9 g of deionized AI4083 (purchased from H. C. Starck, as deionizedAI4083) was added with a total amount of 10 grams of lithium salt ofAmberlyst 15 in 24 hours. The mixture was stirred during the entiretime. The mixture was filtered and the pH of the collected filtrate wasdetermined to be 3.2.

Sample Comp. 5-C

58.18 g of deionized AI4083 was added with a total amount of 14 grams ofbarium salt of Amberlyst 15 in about 18 hours. The mixture was stirredduring the entire time. The mixture was filtered and pH of the collectedfiltrate was determined to be 3.4.

Sample Comp. 5-D

Deionized AI4083, which should be free of sodium, purchased from from H.C. Starck GmbH was used for conversion to the tetra-butyl ammonium salt.50.96 g of the deionized AI4083 was added with a total amount of about 9grams of the tetra-butyl ammonium salt of Amberlyst 15 in 20 hours. Themixture was stirred during the entire time. The mixture was filtered andthe pH of the collected filtrate was determined to be 4.3.

Similarly, samples of AI4083 were treated with lithium and cesiumion-exchange resins to result in two additional series of samples withpH values greater than 1.8.

Example 21

This example illustrates the performance of OLEDs made with bufferlayers made from the dispersions of Examples 16-21 and ComparativeExample 5.

The devices were made in a manner similar to that described in Example6.

The following EL polymers were used:

Name Polymer Type Manufacturer Super Yellow PPV Covion Blue BP79Polyfluorene Dow Green K2 Polyfluorene Dow AEF 2198 Polyspiro Covionwhere “polyspiro” refers to a polymeric spiro-bifluorene.

FIGS. 8( a) through 8(c) show the initial device performance of PLEDsthat contain a PEDT/PSSA buffer layer, that has had its pH adjusted.Clearly, increasing the pH of Baytron-P much above 2.5 significantlydegrades the performance of OLED devices. FIGS. 8( a) and 8(b) compareBaytron-P AI 4071, and Baytron-P 4083, two similar products but withdiffering electrical conductivity. They have both had their pH adjustedusing a sodium ion-exchange resin. FIGS. 8( c) and 8(d) show thatlithium and cesium ion-exchange resins, respectively, cause the samephenomenon to occur.

FIGS. 9( a) through 9(c) show the initial device performance of OLEDsthat contain a PEDT/Nafion® buffer layer, that has had its pH adjusted.Unlike the devices containing PEDT/PSSA, these devices are not degradedby a pH neutral buffer layer.

In order to assess operational lifetime, the devices were operated witha constant DC current to give an initial luminance of 200 cd/m², andplaced in an oven at 80° C. in order to accelerate their degradation.The devices were constantly monitored for changes in their light-outputand operating voltage. Operating lifetime was defined as the time forthe luminance to drop to half of its original value (i.e. to 100 cd/m²).The results are given in Table 3 below.

TABLE 3 Device Operating Lifetime Lifetime in Hours Buffer EL pH ofBuffer Layer Layer Polymer 1.8-2.0 3.2 3.4 3.8-4.3 6.8-7.0 PEDT/NafionSuper 200-250 200-240 Yellow PEDT/Nafion Green K2 900-1100 900-1100900-1100 PEDT/Nafion AEF2198 300-400 400 PEDT/PSSA Super 200-250 46 4 **** Yellow PEDT/PSSA Green K2 400 ** ** ** indicates that the device doesnot light

Clearly the PEDT/PSSA devices give good lifetime only for a narrow pHrange (pH<˜2.5), whereas the PEDT/Nafion® devices can operate over amuch wider pH range (at least pH 1.8-7.0).

Example 22

This example illustrates that PEDT/Nafion® does not etch ITO contacts.

An ITO test substrate was prepared as follows: A glass substrate coatedwith ˜1300 angstroms of ITO was obtained form Applied Films Inc. The ITOlayer was etched into a stripe pattern with ITO stripes 300 micronswide. These stripes extended the full depth of the ITO layer, so thatthe substrate glass was exposed between the stripes. These stripes hadwell defined edges. A Tencor profilometer, with a vertical repeatabilityof ˜10 angstroms was used to measure the height of the ITO stripes.Samples were immersed in CH8000 or PEDOT:NAFION at room temperature, forvarious times. Prior to measuring the ITO thickness the samples wererinsed in DI water and plasma ashed for 15 minutes to remove any organicresidue. In each case ITO thickness was measured for 4 stripes on 2separate substrates, giving a total of 8 data points for eachmeasurement. The PEDT/Nafion® solution was prepared as described inExample 7 and had a pH of 3.8. The PEDT/PSSA solution was Baytron CH8000, with a pH of about 1. The results are shown in FIG. 10. Note thatafter 24 hours of immersion in PEDT/PSSA the ITO thickness was reducedby ˜1%. This was clearly visible in the optical interference color ofthe ITO film. In device manufacture, the exposure of ITO to liquidPEDT/PSSA typically lasts only a few seconds. However, the residualmoisture in the PEDT/PSSA film will perpetuate the corrosion of the ITOthroughout the lifetime of the device. The dissolution of 1% of the ITOlayer will generate high concentrations of indium and tin ions in thePEDT/PSSA layer.

Example 23

This example illustrates compatibility of aqueous PEDT/Nafion®dispersion with PEDT/PSSA.

PEDT/PSSA (Baytron-P, grade AI4083) was selected for testingcompatibility with aqueous PEDT/Nafion®, from Example 16. Aqueous blendsfrom 95:5 PEDT/Nafion®:AI4083 all the way to 5:95 PEDT/Nafion®:AI4083were made. All dispersion blends were found to be homogeneous and notphase separated. These blends are useful for the fabrication of OLEDs,and other electrically active devices.

Example 24

This Example illustrates the fabrication and performance enhancement ofcolor OLED displays using common cathode metals and common buffer layerpolymers for all colors.

OLED devices were fabricated as follows: 30 mm×30 mm glass substrateshaving a 15 mm×20 mm ITO area were cleaned with solvents and oxygenplasma. The ITO layer was 100-150 nm thick. The aqueous buffer (eitherPEDOT/Nafion®, prepared as in Example 16, or Baytron-P CH8000)dispersion was spin-coated, in air, onto the ITO/glass substrates andbaked at 90° C. for 30 minutes in vacuum. The dried film thickness wasin the range 50-100 nm. These substrates were then transferred into anitrogen filled dry box with oxygen and water levels ˜1 ppm. Thelight-emitting polymer, (Red: COVION AEF 2198, or Green: DOW K2, orBlue: COVION HS 670) was spin-coated on top of the buffer layer. Thelight-emitting polymer solution was ˜1% solids in a common organicsolvent such as toluene or xylene. The films were then baked a secondtime at 130° C. for 5 minutes in the dry-box. The thickness of thelight-emitting layer was ˜75 nm. These substrates were then transferredinto a thermal evaporator and the cathode deposited under a vacuum ofapprox. 1×10−6 torr. The cathode consisted of one of the following: (i)˜5 nm Ba followed by ˜0.5 micron of Al, or (ii) ˜5 nm Ca followed by˜0.5 micron of Al, or (iii) ˜5 nm LiF followed by ˜20 nm Ca followed by˜0.5 micron of Al. Finally these devices were removed from the dry-boxand hermetically sealed prior to operational lifetime testing in anenvironmental chamber. The operating-lifetime testing conditions forthese displays were: Initial luminance 200 cd/m2, DC constant current,testing temperature of 80° C. (in order to accelerate the testingprocess). The results are given in Table 4 below.

TABLE 4 Effi- Life Cath- Voltage ciency time Polymer Buffer layer ode(V) (cd/A) (hours) Red CH8000 Ba 4.5 1.4 120 (AEF2198) PEDOT/Nafion ® Ba4.0 1.5 500 Green CH8000 Ca 3.4 3.2-6.8 400 (K2) PEDOT/Nafion ® Ca 3.04.0-6.0 700 PEDOT/Nafion ® Ba 2.8  6.0-10.0 >2,000 Blue CH8000 Ba 4.34.0-4.5 50 (HS670) PEDOT/Nafion ® LiF/ 4.7 4.0-4.5 40 Ca PEDOT/Nafion ®Ba 4.0-4.4 4.0-4.5 150

While the invention has been described in detail with reference tocertain embodiments thereof, it will be understood that modificationsand variations are within the spirit and scope of that which isdescribed and claimed.

Example 25

This example illustrates preparation of a PEDOT/Nafion® dispersion inwater with a co-dispersing liquid. The Nafion® was a 12% (w/w) aqueouscolloidal dispersion with an EW of 1050, made using a procedure similarto the procedure in U.S. Pat. No. 6,150,426, Example 9.

95.41 g (10.89 mmoles of Nafion® monomer units) Nafion® (1050 EW)aqueous colloidal dispersion (12.0%, w/w), 185.12 g deionized water and14.49 g 1-propanol (Aldrich cat#49, 619-7) were massed into a 500 mljacketed three-necked round bottom flask. The mixture was stirred for 10minutes before addition of 0.421 ml of Baytron-M dioxythiophene monomer.It was stirred for about 1 hour before addition of ferric sulfate andammonium persulfate. A stock solution of ferric sulfate was made firstby dissolving 0.0722 g ferric sulfate hydrate (97%, Aldrich cat. #30,771-8) with deionized water to a total weight of 21.44 g. 4.47 g (0.0452mmoles) of the ferric sulfate stock solution and 1.65 g (7.23 mmoles)ammonium persulfate were then placed into the reaction flask while themixture was being stirred. In the final polymerization liquid, the ratiobetween water and 1-propanol was 9 to 5. The polymerization was thenallowed to proceed with stirring at about 20° C. controlled bycirculation fluid. The polymerization liquid started to turn blueimmediately. The reaction was terminated after 17 hours by adding 13.89g Lewatit® S100 and 13.89 g Lewatit® MP62 WS. The two resins were washedfirst before use with deionized water separately until there was nocolor in the water. The resin treatment proceeded for 5 hrs. Theresulting slurry was then suction-filtered through a Whatman #54 filterpaper. It went through the filter paper readily. The solid % was about4.5% (w/w) based on added polymerization ingredients.

The pH of the PEDOT/Nafion® dispersion was determined to be 5.3 with a315 pH/Ion meter from Corning Company (Corning, N.Y., USA). The surfacetension of was determined to be 41.9 milli Newton/meter at 20.6° C. witha FTA T10 Tensiometer Model 1000 IUD (KSV Instruments LTD, Finland). Thesurface tension was much lower than that (˜73 mN/m) of aqueousPEDOT/Nafion* made without a co-dispersing liquid, as in Example 7. Thedispersion was tested for filterability. 40 ml of the dispersion wentthrough 0.45 μm HV filter (Millipore Millex-HV 25 mm, Cat. # SLHVR25KS)without changing a filter. It was also noticed that the viscosity wasconsiderably lower than that of a same solid % made without aco-dispersing liquid judging from fluid flowing appearance.

What is claimed is:
 1. A stable colloid particle containing compositioncomprising a continuous liquid aqueous medium having dispersed therein apolydioxythiophene and at least one colloid-forming fluorinatedpolymeric acid, and further comprising an additional material selectedfrom the group consisting of polymers, dyes, carbon nanotubes, metalnanowires, coating aids, organic and inorganic conductive inks andpastes, charge transport materials, crosslinking agents, andcombinations thereof, wherein said polydioxythiophene has the structure:

wherein: R₁ and R₁′ are each independently selected from hydrogen andalkyl having 1 to 4 carbon atoms, or R₁ and R₁′ taken together form analkylene chain having 1 to 4 carbon atoms, which may optionally besubstituted by alkyl or aromatic groups having 1 to 12 carbon atoms, ora 1,2-cyclohexylene radical, and n is greater than about 6; wherein thecomposition does not re-disperse in an aqueous medium after it has beendried.
 2. A composition according to claim 1, wherein R₁ and R₁′together form an alkylene chain having 1 to 4 carbon atoms.
 3. Acomposition according to claim 2, wherein said polydioxythiophenecomprises poly(3,4-ethylenedioxythiophene).
 4. A composition accordingto claim 1, wherein said colloid-forming fluorinated polymeric acid isselected from polymeric sulfonic acids, polymeric carboxylic acids, andpolymeric phosphoric acids.
 5. A composition according to claim 1,wherein said fluorinated polymeric acid comprises a polymeric sulfonicacid.
 6. A composition according to claim 5, wherein said polymericsulfonic acid is perfluorinated.
 7. A composition according to claim 5,wherein said polymeric sulfonic acid is a perfluoroalkylenesulfonicacid.
 8. A composition according to claim 7, wherein said polymericsulfonic acid is perfluoroethylenesulfonic acid.
 9. The composition ofclaim 1, wherein the colloid-forming fluorinated polymeric acid includesa highly fluorinated carbon backbone and side chains represented by theformula—(O—CF₂CFR_(f))_(a)—O—CF₂CFR′_(f)SO₃X wherein R_(f) and R′_(f) areindependently selected from F, Cl or a perfluorinated alkyl group having1 to 10 carbon atoms, a=0, 1 or 2, and X is H.
 10. The composition ofclaim 1, wherein the additional material is a conductive polymerselected from the group consisting of polythiophenes, polyanilines,polyamines, polypyrroles, polyacetylenes, and combinations thereof. 11.An organic electronic device having at least one active layer made froma stable colloid particle containing composition comprising a continuousliquid aqueous medium having dispersed therein a polydioxythiophene andat least one colloid-forming fluorinated polymeric acid, and furthercomprising an additional material selected from the group consisting ofpolymers, dyes, carbon nanotubes, metal nanowires, coating aids, organicand inorganic conductive inks and pastes, charge transport materials,crosslinking agents, and combinations thereof, wherein saidpolydioxythiophene has the structure:

wherein: R₁ and R′₁ are each independently selected from hydrogen andalkyl having 1 to 4 carbon atoms, or R₁ and R′₁ taken together form analkylene chain having 1 to 4 carbon atoms, which may optionally besubstituted by alkyl or aromatic groups having 1 to 12 carbon atoms, ora 1,2-cyclohexylene radical, and n is greater than about 6; wherein thecomposition does not re-disperse in an aqueous medium after it has beendried.